Sunday 18 August 2019

Pink-flowered peas (Alderman x Salmon Flowered)

It was more than a decade ago that I made a cross between Alderman and Salmon Flowered, two heritage peas, with the vague dream of producing a good tasting culinary pea with pink flowers. But as my other three major pea-breeding projects took up more and more of my time, it kind of went by the wayside.

Just to recap: Alderman is a tall, elegant shelling pea with white flowers, introduced in 1891. Its flavour is outstanding, which is probably why it's one of the only Victorian tall peas which is still commonly available today. It's far and away my favourite shelling pea, and while there are a few others which can rival it for flavour when they're young, Alderman stays exquisitely delicious even when the peas are at full size and maturity, and I haven't found anything else that can match it. It has large, well-filled pods on large plants, its only disadvantage (if you consider it a disadvantage) is that it's quite late maturing. Salmon Flowered is a real rarity, whose seed I got from the Heritage Seed Library many years ago. It's an umbellatum-type pea, which means it has a heavily fasciated (thickened) stem with all the flower buds borne in a great clump at the top. The flowers bloom more or less all at once and the pods form in a big clump, sticking out in all directions. There were a few of these varieties around in the 19th century but they're no longer commercially available – and in terms of flavour and yield they can't really compete with modern varieties. But Salmon Flowered (not its real name, which has been lost*) has really beautiful and unusual bicolour pink flowers which I haven't seen in any 'normal' pea at all. The wing petals are a peachy salmon pink and the standard is a very pale blush pink.

*A Swedish heritage pea called Rosakrone is now available from Real Seeds and is very, very similar to Salmon Flowered. I grew some Rosakrone this year to see just how similar it was, and while I'd say it's not absolutely identical, it is similar enough that they're most likely different stocks of the same original variety. The pink flowers are very much the same colour.

So the purpose of hybridising Alderman with Salmon Flowered was to see if I could breed the pink flower trait into a crop of otherwise normal garden peas – using Alderman as the benchmark because of its exceptional flavour.

Back in 2010 I grew out the F1 seeds from my Alderman x Salmon Flowered cross and wrote about it here. The F1 plants all had bicolour purple flowers, which might seem like an absolutely bizarre thing to get from a cross between a white flowered and a pink flowered pea, but actually it's what I'd expected. Purple bicolour is the ancestral default flower colour for peas (not just culinary peas but also the sweet pea Lathyrus odoratus) and the only reason why most garden peas DON'T have purple flowers is that they've all been bred to have a recessive gene which suppresses the production of anthocyanin pigment in the plant. I went into some detail about that in my original post about this cross, so I won't repeat it all here, but suffice to say that Alderman's pure snow white blossoms are not due to any 'white flower' gene as such, they're caused by the presence of this gene which switches off the expression of purple colour so that the flowers are white by default. Salmon Flowered doesn't carry this colour-suppressing gene – it can't do, or it wouldn't have pink flowers – so when you make a cross between a variety which has the pigment-suppressing gene and one which doesn't, the F1 generation will default to the dominant condition – which is for colour to be expressed. Being the dominant ancestral trait, purple flowers prevail. But on a genetic level, the recessive half of the gene pair, which forces the flowers to turn white, is still there and ready to be passed on to a large proportion of the F2 offspring.

I only have a modest sized garden and very limited free time so the focus on my breeding for coloured pods (edible fibreless coloured pods at that) took up more attention and space for the next few years and the Alderman x Salmon Flowered went by the wayside. I had the bag of F2 seed which I produced in 2010, but hadn't sown them. So this 2019 crop was another "back from the dead" miracle story.

I found the F2 seeds in a box, and thought about how nice it would be to work on breeding for flower colour for a change, rather than pesky pod colour. But seeds from 2010 were only fit for the bin, surely? I had to do a quick test though rather than lob them straight out, so they went into a tray of water, alongside some other decrepit sideline projects.

I don't normally soak pea seeds or recommend soaking pea seeds. I was doing it here because it was just a germination test on 9-year-old seeds, and they were not expected to sprout. However, almost all of them did.

This goes against everything I've been taught about pea seeds. 1-2 years is commonly given as a pea seed lifespan. Some people report them lasting a bit longer if you store them in the fridge or the freezer. But mine hadn't had any special storage conditions. They were in plastic bags inside a cat food box on top of my bookcase. The 16 seeds (of quite diverse size and colour, being F2s) in the top right of the photo above became 16 sprightly little plants in a frame in the garden.

I didn't see any loss of vigour from the seed being nine years old. In fact one of the plants turned into the most productive pea I've ever grown, producing large numbers of pods on a multitude of sideshoots. That one will be covered in another blog post later, along with a couple of other interesting things which emerged from this growout.

I labelled the plants individually and numbered them from 1 to 16, and took notes on them as they grew, paying particular attention to the colour and density of the axillary pigmentation (the pinky purple splodges where the leaves join the stem) as I've increasingly noticed a significant correlation between axil splodges and the eventual flower colour and/or pod colour.

Well, I already knew that the F1 had produced purple flowers, so what was I expecting to get from the F2? In a sample size of only 16, I wouldn't expect to get perfect Mendelian ratios for anything, but still there are general trends to look out for. The first would be the colour-suppressing gene discussed above. That should, in theory, turn up as white flowers in about one in four of the F2 plants. In the event, I only had one plant with white flowers (plant no.7), but that's enough to show that the inheritance of that trait is working as expected. In this project, the colour-suppressing gene is not what I want, and I will have to select against it in future years as well, as it will be lurking as a hidden recessive in many of the other plants even though they didn't have white flowers.

Of those which showed coloured flowers, I was expecting a majority to have purple bicolour flowers like the F1, as that's controlled by dominant genes and is the trait most likely to express itself. I know very little about the genetics behind pink flowers in peas, if I'm honest, but I was pretty sure it would be a recessive trait and so I had my fingers crossed that it would turn up in a proportion (maybe one in four) of the non-white plants.

And voilà!

It actually turned up in exactly four plants, numbers 3, 6, 10 and 15, which is close to being a Mendelian ratio. These all produced flowers which were a very consistent shade of pink, that is, they were all bicolour pinks with peachy salmon wings and a pale blush pink standard. There was no variation in the expression of the pink colour, other than some differences in how the colour changed over time as the pigment broke down in the fading flowers, where some turned a more dusky, rosy pink than others. But in terms of the essential flower colour, they were identical to one another and identical to the colour of the parent plant, Salmon Flowered, which provided the pink gene. They did all have somewhat larger flowers than Salmon Flowered – flower size was more consistent with that of Alderman – but that's controlled by a different genetic locus.

They were absolutely beautiful and I was thrilled with them.

A second recessive trait which I was expecting to show up in one in four plants was the umbellatum form – which as far as I know is a simple recessive gene which causes the flowers and pods all to bunch together in a cluster on top of a fattened stem. But having never done breeding work with umbellatum-type peas before, I couldn't be sure how this would work out in practice. Again though, it turned out much as predicted. Only two plants, plants 5 and 9, were of the umbellatum type, which is a bit short of a Mendelian ratio but close enough to show the principle of it. There were no intermediate types, all the plants were either umbellatum or non-umbellatum. As far as this project is concerned, the umbellatum trait is not a desirable one and so I'll be having to select against it until all the hidden recessives are eliminated from future generations. The two plants which had this trait were both purple flowered anyway. It may not be a desired trait in this cross but it does look quite spectacular!

All of the pink-flowered plants had what you might call 'normal' form. They produced two large flowers per node, which gave rise to large green pods, much like Alderman. The umbellatum types did tend towards very slightly smaller pods, whereas all the non-umbellatum types had normal size pods, which suggests that smaller pods are a byproduct of the fasciation trait in umbellatum peas. It may simply be that the plant doesn't have enough energy to produce the flowers and pods all together at the same time without compromising on size a little bit. If there was a genetic cause, i.e. a gene in Salmon Flowered which made its pods smaller (as they ARE quite small) then I would expect that trait to segregate randomly through the F2 plants – but it didn't.

Axillary pigmentation is another interesting one. It occurs in all (in my experience) peas with coloured flowers. A purple-pink splodge at the point where leaf meets stem is invariably seen in a plant with purple bicolour flowers. The purple blotch is made from anthocyanin pigment, so it's subject to the action of the same colour-suppressing gene which causes white flowers. A pea with white flowers will have no pigment in the axils at all, because this gene switches off all production of anthocyanin pigment throughout the whole plant. So in a cross between a white-flowered and a coloured-flowered pea, like this one, the presence or absence of colour in the leaf axils is a very early indicator of whether the plant will eventually have white or coloured flowers. The axil pigment usually shows up quite early in the seedling stage, when they've produced their first couple of sets of true leaves.

In the case of this hybrid, the Salmon Flowered parent variety has an unusual kind of axillary pigmentation. It's lighter than the usual type – in fact it's a dusky rose pink, and very soft and subtle. I was thinking it's probably not a coincidence that a variety with unusual pink flowers also has unusual pink axillary pigmentation – there's probably a meaningful correlation between the two. So I was watching my F2 seedlings to see if there was any sign of this correlation, and there was.

The photo shows the subtle dusky pink pigment in the axil of ASF 06, one of the pink-flowered phenotypes. All the other pink-flowered ones had this as well, while the purple-flowered ones had the more normal blotch of purple colour in the leaf axils, and the white-flowered plant had none at all, as expected.

This is bloody useful, actually. If the colour in the leaf axil is a reliable indicator of flower colour, which it does seem to be, subject to errors of interpretation when the shade is a bit ambiguous, then it means you can identify the flower colour a good month or two before they flower.

Right then, so the appearance of pink flowers in roughly a quarter of the F2 plants suggests a fairly straightforward recessive gene at work. I'm sure there is some info out there somewhere about how this works, but the details of which genes control which traits are often buried in papers in academic journals which I don't readily have access to – and even when I do get hold of them, I struggle to make sense of the scientific jargon and it makes my brain hurt. So in my layperson ignorance I'm going to make a speculative guess about what's happening with this pink flower business.

I think that a pink-flowered pea is essentially a purple-flowered pea which has come under the influence of a modifier gene – probably just a single, recessive modifier gene. I think this modifier gene acts on the chemical makeup of the anthocyanin pigment, suppressing the production of blue pigment while leaving red pigment unaffected, so that the flower comes out pink instead of purple.

There are two reasons why I think that. The first is to do with the axillary pigmentation. If there was a gene specifically coding for pink flowers, I can't see why it would affect the colour of the axils as well. But clearly it does, because pink flowers and pink axils go together. Which suggests a modifier gene having a blanket effect on anthocyanin production throughout the whole plant.

The second reason I think this is the case is because of a study which has been done on sweet peas, which are a different genus from edible peas but have a lot in common with them. As I mentioned earlier, the default ancestral colour for sweet peas is a purple bicolour, but some time in the 18th century a mutation occurred which gave us the lovely pink-and-white bicolour known as Painted Lady, which is still widely available today. A study was published in 2017 in the Canadian Journal of Plant Science on the genetic basis of this mutation, and although I don't have access to the paper itself there was enough information in the abstract to tell me what I needed to know: a single base pair mutation means that the flower is lacking the blue pigment known as delphinidin, which is one of the anthocyanins which make up the purple colour in sweet peas. In the absence of delphinidin, the flower becomes pink. In simple terms, if you imagine that the colour of the purple flower is made from layers of translucent blue and pink, removing the blue layer leaves you with just pink.

So that's what I think is probably happening in Pisum sativum as well. If you look at the pink flowers in my F2 plants, they are all bicolours. They are all essentially the same, there's no variation in the colouring. So it seems quite plausible that they are meant to be the default purple bicolours, and that a recessive gene has come along and deleted the production of delphinidin (or whatever blue pigment they're supposed to have) and this salmon-pink bicolour is the result.

As I said, this is just my speculation! I'm sure there are people out there who know more about it than me.

This is turning into a very long post, but I have learned such a lot from growing these sixteen F2 plants!

So let's finish up with a bit about the pods and peas. This project is not seeking to produce edible pods or coloured pods: both parents are green-podded shelling peas, and all the offspring are green-podded shelling peas as well. My aim was to get the kind of big, plump green pods and fat peas found in Alderman, and not so much of the small pods and small peas of Salmon Flowered. In this, the F2 generation has given me what I wanted, because all the non-umbellatum type plants produced pretty good pods and most had good sized peas.

I did some taste tests as well. I was hoping to get as close as possible to the sweet and complex flavour of Alderman and not so much of the pleasant but rather mealy taste of Salmon Flowered. In this I was also very lucky. I tasted three out of the four pink-flowered phenotypes and they all had very good tasting peas, with ASF 06 being the best. Unfortunately ASF 10, which was a lovely plant with beautiful flowers, died prematurely after getting its main stem damaged in a storm. It had only just begun setting pods at that stage and the peas inside were still very immature. I thought I had nothing to lose by leaving the pods on the plant as long as possible in the hope that they would use the residual energy of the plant to carry on maturing a bit. And they did. When I finally harvested the pods, the peas were still quite small but they look like they might, just might, be mature enough to germinate. I didn't eat any of these – I wanted to conserve as many as I possibly could.

Here are the seeds from the four pink-flowered plants after being harvested and dried. As you can see there are a few differences between them. They all have subtle purple speckles on them, except for the salvaged seeds of ASF 10, which were not fully mature. ASF 15 has more of a green colour to its seeds, while ASF 06 and ASF 15 have a mixture of green and tan. The tan seeds are a trait inherited from Salmon Flowered, which also seems to be related, albeit loosely, to the pink flower trait. You may also notice that ASF 06 in particular has some variation between wrinkled seeds and rounded, dimpled seeds. The wrinkled ones are a rule-of-thumb indication of sweetness in peas, because sugar shrinks more than starch does. I probably won't select out the wrinkled ones next year though, I'll grow a bit of both, but I might possibly separate them out into different halves of the seed tray so that I can keep track of whether there's any correlation between wrinkled seeds and sweeter flavour.

That's it now, until next year when I can grow the F3. I would expect all four of the pink-flowered peas to breed true for the pink colour, as it's a recessive trait and they must be homozygous for that trait. It's likely that some of the purple-flowered phenotypes are heterozygous for pink flowers, and will produce a few of them in their offspring – so I will probably grow out some of the best of those to see if I can get some more pinks. But either way, I'm extremely pleased with what has come out of this F2 crop and I'm feeling quite optimistic about the prospect of getting peas with pink blossoms and lovely flavour, within a couple more years.

Friday 9 August 2019

Red-podded pea update: the F6 crop and beyond

Ever since I first had a red-podded pea turn up (completely unexpectedly) in a breeding project in 2008, I’ve had a bit of a frustrating time trying to get it into a form which is worth releasing into the world. Not that I’ve been trying continually, because I haven’t been able to maintain the garden every year during the last few years, but it has had me scratching my head trying to come up with a way of producing edible pods with this rich crimson colour. Finally, in 2019, I had a significant breakthrough.

The original red-podded pea plant, numbered GSC 15 in my breeding project, was an F2 from a cross between Golden Sweet and Carruthers’ Purple Podded. The purpose of the cross was to breed a new purple mangetout pea for Ben Gabel at Real Seeds, but neither Ben or I had any idea that crossing a yellow pea with a purple one would result in a red colour. It was only this one plant which produced red pods, and it happened because it was a yellow-podded pea with a solid layer of purple pigment on top. The pigment is translucent, so the yellow shining through from under the purple creates a beautiful glowing red, like stained glass.

This breeding line, which is currently somewhere around an F6 or an F7, is now a stable, true-breeding variety. It’s reliable and consistent for all its traits, except one: it still turns up a small minority of offspring whose pods are not fully red. It doesn’t tend to throw any plain yellows any more, at least not in the growouts I’ve done, but it will produce some semi-red plants which look like the red pigment has just been sprayed around the edge, and some which have a jagged, flamed pattern of solid red on a yellow background. I think these are caused when one or other of the two dominant genes for purple pods is unable to express itself. But WHY it can’t express itself I don’t really know. All I know is that it happens often enough to be a thing, and on that basis I don’t think the semi-reds will cease appearing no matter how many years are spent trying to rogue them out. They just have to be accepted as the nature of the beast, and besides, I had one semi-red this year which I liked enough to want to keep it, if I can persuade it to become a variety in its own right.

One of the semi-red phenotypes. I believe it's probably caused by co-dominance between purple and non-purple genes. Because of that, no amount of 'roguing out' will eradicate these oddities, which show up in a small minority of offspring.

But anyway, having reached the F6 generation this stable red-podded variety still has a problem, and the problem is not going to go away. It doesn’t taste good, either as a shelling pea or a mangetout. It has a gristly layer of fibre inside the pod which makes it unsuitable for eating even when it’s small, and if you shell out the peas to eat fresh they are starchy as hell, with a bitter aftertaste. The genes controlling flavour in peas are complicated, but the situation here is very simple – it is true-breeding for crap flavour.

It does, however, look truly stunning.

It’s possible that it will find a use as a soup pea, maybe becoming edible when it’s dried and then boiled for ages. The jury’s still out on that one. But in its current form it’s not suitable for unleashing on the world, and will have to be considered a breeding line. To that end, I grew out a batch of seeds in 2019 which had been in storage for 4 or 5 years, just to replenish my stock of seed. I saved seeds from the best ones (which was most of them, as it’s certainly a fine-looking variety) and saved the rest for taste-testing in the kitchen, some time when I can be arsed to boil up a vat of pease pudding.

So, what to do? I need red-podded peas with edible pods. And ones which taste nice.

When I did my initial report on the edible-pods frustration nearly ten years ago, I said there were five things I could do about it. Here they are again, with the results of my efforts.

1. Stand in the middle of the garden and shout "BOLLOCKS!" in a really loud voice. Yep, done that.

2. Grow out the remaining F2 seeds (about 20 left) in the hope of finding another red-podded phenotype but with edible pods. This didn’t provide what I was looking for, but I did find an extremely nice purple mangetout (the whole point of the breeding project in the first place) which I selected and re-selected in the F3 and named Barcarolle.

3. Grow out the remaining F1 seeds to get more F2 seed. I tried this, as part of a belt and braces approach. Growing out more of the F1 took a year but it yielded plenty of seed. I grew a batch of F2s in 2019 and some of them were quite nice but no, I didn’t get the tasty-edible-red-podder I wanted.

4. Switch to another line of F3 seed, even though none of them are proper red-podders. This was always a good bet, because some of the necessary traits for red mangetout pods are recessive genes which may be hiding in the DNA of a plant which isn’t showing it. For example, yellow is the base colour for red pods and you can’t get red pods without the recessive ‘golden pod’ gene known as gp. The laws of probability suggest that two out of three of the F3 lines should carry the gp gene, even though they don’t themselves have yellow pods. Also, the two genes which produce edible (fibreless) pods are both recessive, so a goodly proportion of inedble-podded lines could produce edible-podded offspring.

Although only one of my original batch had properly red pods, I did get a couple of peachy-coloured or semi-red mangetout lines. My efforts revolved around these, as they were so “nearly there” – they had sweet-flavoured edible pods and a beautiful fiery blush. But sadly the fully red colour didn’t show up in their offspring either.

But although I didn’t get anywhere with the ‘peachy’ F3 lines, it was another F3 line which gave me my breakthrough in 2019, in a completely unexpected place: my Barcarolle purple mangetouts.

5. Grow more of the original red-podded F2 and cross it with something else. I tried a lot of this as well, but it's the most time-consuming option and I don't have many results yet, so I’ll report on it another time.

Barcarolle purple mangetout
Right then, this is what happened with the breakthrough. Alongside my growout of red-podded peas this year, I planted 16 seeds of my newly developed purple mangetout. Sixteen plants is not very many, but I’m doing all my breeding work on a very small scale in my back garden, so that’s all I have room for.

Barcarolle is a very promising variety which originated from the same cross as the red podders – Golden Sweet x Carruthers’ Purple Podded. I selected an F2 plant a few years ago which had beautiful dark velvety purple pods – a really solid dark purple, which is not something you get all that often in peas. As the peas start to swell inside the pod, they bulge through the pod wall and look like a row of little blackcurrants. The reason this happens is because there’s no fibrous membrane inside the pod, like you’d get with a shelling pea. It takes two recessive genes to get the pod walls completely fibreless like this, and it’s a desirable trait to have because it means the pods are fully edible at all stages of development – they don’t go coarse and gristly. I also got lucky with the flavour, as the pods tasted sweet and juicy and were pretty much stringless. Again, this is an uncommon thing to find in a purple-podded pea, because the purple colour is often associated with a slightly bitter flavour. It’s not that the pigment itself is bitter tasting, but there’s some kind of gene linkage going on which means that the purple pod genes are usually inherited alongside some less-desirable flavour genes. This was by far the best purple podded pea I’d ever tasted so I was well chuffed with this plant.

The following year I grew out the F3 generation, and to my delight, it came almost completely true to type. I had expected a few unwanted recessives to show up, but they didn’t. The F3 plants were as uniformly purple and bobbly and sweet and juicy as the previous year’s plant. I don’t always name my breeding projects at this relatively early stage, but it seemed like it was going to be quick and easy to make it into a stabilised variety so I gave it the name Barcarolle. (In case you’re wondering, I play the piano and I’m a big fan of Chopin.)

So then I grew out this batch of F4 plants in 2019, and, well, to say they began to segregate is an understatement. They segregated like buggery. Fortunately they all had the bobbly edible pods (a recessive feature), but they varied in size, flavour, number of pods per node, and most of all they varied for pod colour. In my batch of 16 plants, I ended up with four different pod colours – purple, green, yellow and red!

My 2019 crop of Barcarolle F4 purple mangetouts, segregating for four different pod colours ... aaargh!

I must admit I don’t quite know why this happened. It doesn’t make sense for a variety which is true-to-type in the F3 to suddenly start segregating like mad in the F4. The most likely explanation, I think, is that I happened to grow out (by chance) only seeds which were heterozygous for pod colour in the F3 generation, so they all showed the dominant purple colour but they still had the recessive genes squirrelled away in their genome. Given that I work with such small sample sizes, this is entirely possible. But anyway, who cares – the thing that matters is that I ended up with no less than four red-podded plants, all of them with lovely juicy edible pods. This is such a holy grail for me, some 13 years after I made the original cross, that I spent an awful lot of time just standing in the garden gawping at it.

The purple pods on the left are what Barcarolle is supposed to look like, but it came out with these red podded variants as well.

In some ways I probably shouldn’t be surprised to be getting red pods segregating out from Barcarolle. The only difference between red pods and purple pods is the base colour of the pod – green for purple-podders and yellow for red-podders. Barcarolle is derived from a yellow-podded parent, so the presence of the recessive gp (golden pod) gene shouldn’t be a surprise. I might have saved myself some grief if I’d tried looking for it here earlier.

As well as being exactly what I’ve been looking for for the last decade, the Barcarolle red-podders have some other advantages over my original red-podded pea. The red colour itself is a bit brighter – more scarlet than crimson. Both colours are equally nice when the pods are young, but one slight flaw in the original variety is that the red tends to darken as the pod matures, until they start to look purple rather than red. The reason for this is not a change in the pigment itself, it’s because of the natural darkening of the base colour of the pod. As yellow pods age, they tend to go more green – a trait seen in the parent variety Golden Sweet – and a greener pod means the pigment appears more purple. In the Barcarolle-derived red-podders, the pods stay yellow right through to maturity, and so the pigment continues to look red for a lot longer. I don’t know what subtle genes are responsible for this difference, but it was consistent across all four of the plants in this batch.

The best of them was the plant known as BRC 16 (above), which was hugely productive. It grew to around 7ft tall and not only produced two pods per node, it also developed fully productive sideshoots – a rare thing in peas – and bore good quality pods on those as well. It also did very well in the looks department, having beautiful colour-changing flowers borne on stems with a lot of bright scarlet colour and pretty pink mottling on the calyx. BRC 14 and BRC 06 were both very similar but not quite as vigorous. The best one for flavour was BRC 11 which had a fantastic juicy raw flavour, like apples! 

I do want to develop a red-podded pea which tastes good raw, because the colour is spoiled by cooking. With any red-podded or purple-podded pea, if you cook it any way other than the lightest steaming, the colour just disappears into the cooking water. No amount of careful breeding is going to resolve this, because it’s in the nature of the pigment itself – anthocyanin, which is water-soluble, and that’s just the way it is. So the only thing a plant breeder can do to get around this is to develop varieties which taste so good raw you won’t need to cook them.

Now, of course, I will have to wait until next year before I can grow out the offspring and see how they look. But I’m very optimistic. And I still have the purple-podded Barcarolle line which, once I’ve stabilised it, will be a wonderful variety in its own right. The red-podded line is not named yet, but I have another year or two to think about it.

The Barcarolle-derived red peas have beautiful bicolour flowers which turn blue as they fade, like these on BRC 16.

Saturday 20 July 2019

Sweet pea curiosity

Two different flower colours from the same batch of seed.

One of my favourite sweet peas is a variety called Nimbus, and I grew a couple of batches in the garden this year. It's a widely available variety and (unusually for me, as I mostly use well-off-the-mainstream seed suppliers) I got the seeds from Thompson & Morgan.

Nimbus is a dark purple striped variety ('striped' being the official way of describing this type of colour pattern). Most of the plants in this batch are exactly that. And then there's one which looks like this:

Whereas Nimbus is supposed to look more like this:

So, it's a rogue. It's one of those things which is not supposed to turn up in a batch of commercial seed and which would normally be instantly torn out and bundled off to the compost heap in order to preserve the integrity of the variety.

I quite like it though. So it's not going to be exterminated. I want to find out what it is and what it's doing in a packet of otherwise fairly normal Nimbus seeds. As far as I can see there are four possibilities.

1. It might be a sport, or spontaneous mutation. Sweet peas are very prone to this, so it's a strong possibility.

2. It might be an accidental hybrid, if some stray pollen from another variety 'contaminated' the plants during seed production. This is also possible. Sweet peas normally self-pollinate, but that doesn't mean they can't get crossed accidentally, in some circumstances.

3. It might be an 'off type' or rogue inherent in Nimbus as a variety. In which case, other people have probably come across it as well, and I'd be interested to hear from them.

4. It might be a different variety, which got mixed into a batch of Nimbus seeds by mistake. This is also something that easily happens, and there are one or two other sweet peas which have a similar appearance.

Probably the only way to find out is to save seeds from the rogue plant and sow them next year to see what they do. If it's an accidental hybrid, I will probably get a lot of segregation – which is always a good thing as far as I'm concerned (though it's something which would make many gardeners fling their hands up in horror). Of all the above possibilities, I think no.4 is probably unlikely, because although there ARE magenta/maroon striped sweet peas in existence, this one really does look like Nimbus in every respect other than the flower colour. So I think one of the rogue-of-Nimbus explanations is more likely.

My instinctive feeling is that it's a sport, because it looks to me as though the dark purple colour of Nimbus is made by combining a basic magenta colour with a blue overlay over the top (I say that because some Nimbus flowers show traces of magenta as the flowers fade), so this oddity looks to be the basic Nimbus colour without the blue overlay.

Anyway, I won't know until next year, so here are a few other pictures of my favourite sweet peas in the meantime.

Painted Lady is one of my top favourites, and a little piece of garden history. As a named variety it dates back to at least the mid-18th century, which is quite remarkable, as it pre-dates culinary peas as we know them today. It's also a beautiful, elegant, unassuming variety with a lovely colour and an exquisite scent.

Queen of the Isles is another old variety, one of the first to be bred by the legendary sweet pea breeder Henry Eckford and introduced in 1885. It has red and white flaked flowers.

Matucana is frequently described in seed catalogues as one of the oldest cultivated varieties, but it isn't. In fact it's probably not a heritage variety at all. But it is very lovely, with purple bicolour flowers and a scent second to none.

Thursday 27 June 2019

A trial of ludicrously ancient tomato seeds

This year I decided I wanted to grow some more of a tiny globular red tomato called Tomatito de Jalapa which was given to me years ago by my friend Patrick Wiebe. This is a blight-resistant variety, at least to some extent, which grows quite well outdoors in the UK, and I also love the taste of it, and the tiny, almost perfectly spherical tomatoes. It's not a normal garden tomato, it's a species of wild tomato from South America which is not (to my knowledge) commercially available. Therefore it's quite rare, and you can't buy its seeds in the shops.

When I grew it in the past, I saved seeds from it. Of course I did. But I'm buggered if I know what I've done with them. Somewhere there must be a box of home-saved tomato seeds hiding in a corner of my incredibly well organised house, because there are other varieties I'm missing which I know I've saved seed from. Anyway, when I was sowing my tomato seeds this year, I couldn't find them. I did, however, still have the little baggie of seeds which Patrick originally gave me, and which he'd sensibly labelled with the year they were produced: 2009. So these are 10-year-old seeds. The received wisdom in many gardening books is that old seeds won't germinate, or will produce only feeble plants, but I know this to be bollocks. So I put a bit of compost in a tiny flowerpot and sowed one of Patrick's decade-old seeds just to see whether it would grow. As you can see in the photo above, it did.

I dug out a couple of other geriatric seed packets from my box which I wanted to resurrect. One was an unidentified variety which I call Café Rubik, because I filched the original single cherry tomato from a café in Cheltenham called Café Rubik, in April 2010, after having it arrive on my lunch plate and deciding it was probably the best tomato I'd ever tasted. It must have been an F1 hybrid, whatever it was, because it segregated into three different fruit colours the first time I grew it. That doesn't put me off, of course ... I love to see a bit of segregation so that I have the option to select something new and unique. So Café Rubik the F2 still lives, the seed from that single original tomato (plucked from a salad, no less) still germinating after nine years, long after the café itself has closed down.

Another one I decided to grow out was this ancient packet which I got as a freebie from the Heritage Seed Library. Salt Spring Sunrise, a Canadian heritage variety. God knows how old these seeds are; they're not dated, and I don't remember what year I was sent them. It could easily have been as long ago as 2007. And while the others I sowed had at least been stored in airtight grip-seal bags, these were just in a plain brown paper envelope, stashed in a cardboard box in the spare room. Anyway, I sowed two of these seeds, and one germinated. Initially it did struggle to free itself from its seed husk, and when it finally emerged from the soil it had ripped both its cotyledons clean off! It was left with a pair of green stumps. I didn't think there was much hope of it surviving, but after sitting there fattening up the green stumps for a couple of days, it began to grow its true leaves – and very quickly recovered.

Inspired by the longevity and resilience of these seeds, I thought it might be interesting to do a more formal germination test on some of my other tomato seeds, to find out just how old or craply handled they have to be before they stop germinating. As I never throw anything away, I had no shortage of ludicrously outdated specimens to choose from. I selected six packets of varying ages, which included some purchased seed and some I'd saved myself. Here they are:

Some of the bought seeds were from Association Kokopelli and some were from Terre de Semences, which is what Association Kokopelli was called before it became Association Kokopelli. I haven't purposely singled out this supplier, I just chose them because they're the oldest seeds I have in my collection. The ripest vintage was a pack of Boondocks produced in 1998, which makes them 21 years old at the time of sowing. Close on its heels came the millennium-era seeds of Canabec Rose; a 16-year-old pack of Peacevine Cherry from 2003, and some Anna Russian from 2007. Bringing up the rear were two packs of my own seeds: an F3 derivative of a variety called Pink Jester which I originally bought from a supermarket and saved seeds from, and the special beta-carotene rich orange variety Caro Rich, which I hadn't even saved properly – they were just scraped out of the fruit onto a piece of kitchen roll and left to dry. These seeds are 13 and 11 years old respectively.

The test was not all that scientific. I filled a small 6-module tray with compost, and on 3rd May I sowed two seeds of each variety in the front row (the younger ones), and four each of the varieties in the back row, since the older ones were less likely to germinate. These are very small sample sizes, but I didn't want to sow too many just in case they all grew! I'm emotionally incapable of murdering seedlings which are surplus to requirements, so if I'd ended up with a dozen plants I'd have had to find room for them all somehow in the garden.

The tray of seeds was kept on the windowsill in my music studio, which has a radiator under it, and this was on fairly often as the weather was so bloody cold. This bottom-heated windowsill is brilliant for germinating tomato seeds and it didn't take too long for the first germination.

And the first one up after 10 days was ... Caro Rich!

Then came Pink Jester F3, a couple of days later. Both the seeds of that one germinated, while with Caro Rich it was just one. At 11 years old, Caro Rich was the freshest of all the varieties I sowed, but it was very interesting to me to see it germinating so readily, given that the seeds had been saved in the crudest way. The proper way to save tomato seed is by the fermentation method, which is what I would normally do and recommend, and the simple method of lobbing them onto kitchen roll and letting them dessicate into a disgusting scabby crust is widely frowned upon as a bad way to save tomato seeds. For one thing they stick irretrievably to the kitchen roll, so when you want to sow them you have to tear around them and sow them with some of the kitchen roll still attached. There's also the matter of the germination-inhibitor chemical which tomatoes naturally produce within their gel, which stops the seed from germinating while the gel is there. The fermentation method removes this very effectively; the kitchen roll method doesn't. Though you could argue that at 11 years old, any biochemical inhibitors had probably degraded anyway. I also stored the kitchen roll sheet in a sealed plastic bag after it was fully dried, so that might have helped to preserve it. But still, it was interesting to see this seed germinating normally in spite of everything.

I'd still recommend the fermentation method for most tomato seed-saving, but if you really can't face doing it, or haven't got time, or it's a tiny quantity of seed which is too fiddly to ferment – you should be fine just to splat it onto a paper towel, and still expect to get a decade's worth of viability out of it.

Following these initial germinations I didn't get any more. I kept the trial going for around a month, but nothing else showed up. I took the tray out to the greenhouse and potted up Caro Rich and the two Pink Jester seedlings, all three of which are growing on well. I don't generally find that plants from old seeds are inferior to plants from fresh seeds (though I'm sure some commercial seed companies would like people to think that). They may be slightly slower to germinate and have less available nutrient within the seed to get them through the germination process, but once they've established themselves with a root and a shoot they usually grow pretty normally. The really old seeds in my trial didn't germinate though. Maybe some of them would if I sowed a larger sample. But for now, I forgot about the rest of the modules as I got into my busy season, and they stayed on the top shelf in the greenhouse. Until, seven weeks after I sowed the seeds, I found this:

Yes, it took its time all right, but Anna Russian germinated, at 12 years old. This is a phenomenon that most tomato growers have probably come across, even with much fresher seeds than these: a tray which fails to germinate is cast aside, only to be found sprouting quite happily several weeks later after being completely abandoned and neglected. Sometimes tomatoes just inexplicably won't sprout until they're ready, and they won't be rushed.

Sadly, the day after this photo was taken, Anna was razed off at soil level by a snail. So I won't be growing any of that variety this year. But still – it germinated.

One important observation I made with all of these antique seeds, and not just Salt Spring Sunrise which had the most extreme case of it, is that they were all very prone to getting the seed husks stuck on their heads when they first emerged from the soil. This is not surprising, as the older the seed is, the more it dries out and shrinks. It might be a good idea to try to reconstitute the seed with a bit of moisture before sowing it, to help avoid the problem of seedlings getting completely stuck and unable to release themselves, but I haven't done any experimenting to find out how best to do that. Maybe an overnight pre-soak would be enough.

The message of all this, in summary: don't immediately assume that a packet of old seeds is no longer viable – at least give it a go.

Sunday 22 May 2011

Potato blessings

An unnamed/unidentified South American andigena potato. The carmine-red splodges in the leaf axils give a clue to the deep red tubers it will produce.

So here's some positive stuff I've been getting on with. I've had some very generous potato donations from Rhizowen and Frank Van Keirsbilck, which I'm watching with great excitement as they grow. They include several colourful specimens of South American andigena (I think) types, a rare phureja variety, and some Maori (Taewa) potatoes which Frank grew from seed sent to him by a gardener in New Zealand. Being seed-grown they are "Frank originals" rather than named varieties, but I am happy with that. To me, a reshuffling of the genes of Maori potatoes is just as interesting as getting hold of existing heritage types, because it shows a lot of detail about the ancestry of these potatoes as the various parental traits segregate out. I'm very excited about them as they are very hard to get hold of outside New Zealand. It's a little difficult to tell what the spuds will look like, as all potatoes at this time of year look like brown wizened prunes regardless of what cheerful colours they might have had at harvest, so I will have to wait and see. But one seems to be a dusky ultra-purple and another a reddish bicolour. Among the South Americans there is a similar range of colour loveliness, including an unnamed pink and yellow bicolour and a black and tan bicolour called Puca Quitish. It's going to be a fun year for bizarre-coloured mash in the Rebsie household.

This is Pastusa Amarilla, a phureja-type potato from Owen. As the tubers were small I started them off in modules, where they grew like rockets, and this one had already begun to set some tiny tubers of its own by the time I planted them out.

I've not yet had time to blog about my TPS-grown potatoes from last year, and there's so much to say I don't know where to start. There were lots of fascinating colours and exquisite flavours, and some amazingly high yields considering the plants were seedlings and not grown from tubers. A great many tubers produced by last year's seedlings are now replanted and growing for the first time as tuber-grown plants. Some are HUGE ... in fact the biggest and most vigorous potato plants I've ever grown. This may be down to the fact that freshly created potato varieties are relatively virus-free. The more established varieties, unless you get planting stock which has been "cleaned" in a laboratory, will have become burdened with a collection of energy-sapping pathogens over the years. It could also be an effect of hybrid vigour, but that's probably less of a factor in potatoes than in other plants, because essentially all potatoes are hybrids. Their tetraploid (doubled chromosome) structure keeps their genes banging around like a pinball machine in every seed. Hybrid vigour is the norm in most potatoes, which is why they're such a successful food crop, and you should theoretically only see a drop in vigour if you inbreed them, i.e. grow seeds which have self-pollinated. But in an illustration of how nature likes to raise two green fingers to such predictions, the most rampant batch of triffid-aspiring monster spuds I currently have in the garden is an inbred line from self-pollinated berries of Mr Little's Yetholm Gypsy. These little beauties deserve a whole post of their own as they are wonderful, colourful and precious.

One of the most interesting potatoes-from-seed I have on the go is from a cross of primitive stenotomum cultivars, Pirampo x Khuchi Akita. This is an F3 "novelty line" from Tom Wagner, a cross of two traditional Andean potatoes which are not adapted to temperate zones such as Europe but are still fun to experiment with. I have been erroneously describing them as Bolivian, when in fact only Khuchi Akita is from Bolivia, and Pirampo originates in Peru. Any road, this hybrid is diploid, so it lacks the chromosome doubling which gives cultivated potatoes their big tubers and high yields. It's also limited in its ability to set tubers in the British climate, so I couldn't be sure that the plants I grew from TPS would give me any potatoes at all. But they did give me one very big surprise. They were completely and quite astoundingly blight resistant.

Last September I watched as all the potato haulms in the garden turned brown and rotted, including the ones which I was trialling for possible blight resistance as they had been bred to contain the resistance genes. Fortunately the blight in 2010 was late enough that it didn't curtail tuber production, and I got a good harvest, and was able to simply stand back and watch to see how the blight affected different varieties at different speeds. I had twelve plants of Pirampo x Khuchi Akita, in various parts of the garden, and there was not a speck of blight on any of them. They just sat there defiantly while the plague raged all around them, and then, as a final "sod you" gesture to Phytophthora infestans they put on a second flush of flowers just as I was scraping up the blackened corpses of every other potato in the garden. They were still flowering in October when the first frosts came. Their flowers were beautiful too, have a look at these ...

Pirampo x Khuchi Akita potato blossom, 2010.

I was really surprised, because I wasn't expecting this hybrid to show any blight resistance at all. There are a few species of near-wild Andean potatoes which are blight resistant, but not these; these are technically the same species as normal cultivated potatoes, just a less developed form of it. I'm still not entirely convinced that the resistance is genetic, and will have to see what happens to them this year before I allow myself to get too excited. But it does at least illustrate why I'm keen to experiment with unusual varieties like this.

As it turned out, about half the plants managed to set tubers. This is a pretty good achievement for an Andean landrace type, because they are dependent on daylength, and the long daylength in Europe is completely wrong for them. Consequently they don't start to tuberise until the days shorten in the autumn, by which point they don't have time to do anything before the frosts hit them. What I'm looking for in these plants is the odd one or two which can tuberise successfully in our long summer days. It's one of those things which is self-selecting by default and doesn't require much intellectual input from a plant breeder – if it doesn't tuberise effectively then it can't survive to the following year. Extreme Darwin in action. Another self-selecting trait is the keeping quality, since a short shelf-life is common in Andean potatoes. It's often possible for farmers in South America to grow a continuous cycle of potato crops, perhaps two or three a year, so they don't need to be stored for any period of time. They are just replanted shortly after harvest and off they go again. Can't do that in England though, unless you want to grow a crop of frost-bitten stumps. So I can only regrow the ones which stay alive in storage for six to eight months. This weeded out several of my Pirampo x Khuchi Akita beauties, unfortunately.

The tubers I got from the plants were small, deep-eyed, immensely variable in size (but still small) and not very abundant. However they did come in some absolutely glorious colours and markings, mostly reds, purples and intense carmine pinks.

Alas, this beautiful purple bicolour was among the ones which didn't make it through the winter. I didn't even get a chance to taste it as it was so pitifully low yielding. But I feel blessed to have had it enter my life, however briefly.

This one was a lot more promising. It's a bright red one with yellow eyes, though it doesn't look its best in this shot because it's unwashed. (Washing potato tubers considerably reduces the chance of them keeping over winter.) This was by far the best yielding of the lot - a pretty respectable harvest for a diploid landrace type. Only the largest tubers succeeded in surviving over winter, but survive they did ...

And this is what they look like now, blossoming like mad already. Notice that the flowers are more of a mauve colour than the magenta-purple blossom shown above. The flower colours did vary somewhat between siblings in this hybrid, though they were all somewhere on the mauve to purple spectrum.

Sunday 27 March 2011

Tomatoes of past glory

OSU Blue Fruit
OSU Blue Fruit tomato. Not yet commercially available (to my knowledge), this is a breeding line of purple-black tomatoes developed at Oregon State University in the US. The fruits ripen to a deep coal black but are perhaps at their most beautiful during the ripening phase when they take on some magnificent purple tones. The flavour is decent enough, although work is still being done to improve it. And no, they are not genetically modified: the colour was achieved through traditional breeding methods by combining three genes found in South American wild tomatoes.

I have been rather quiet on the blogging front haven't I? The reason is that I'm now working full time for a small publishing company, and also writing a book about potato breeding which will be available in late summer or early September. The book will answer all your questions about growing from TPS and potato seed saving, and to the best of my knowledge will be the first book of its kind on the subject. It's all very exciting and enjoyable, but as you can imagine I am immensely and obscenely busy, and working some very long hours.

Today however, I'm closeted indoors as it's the first warm and sunny weekend of the year and that inevitably means the neighbours are having a barbecue. There's nothing like the stench of burning flesh to send me scuttling back into the house with all the windows shut; so here I am, and may as well do something useful like posting some of the tomato pictures I took last year and didn't get round to using for anything. All of these were grown in the greenhouse unless otherwise stated.

Darby Striped Pink/Yellow
Darby Striped Pink/Yellow. This came from the Heritage Seed Library and is an absolute corker. It's actually an English-bred tomato, from the breeding work of Lewis Darby at the Glasshouse Crops Research Institute in Littlehampton in the 1950s and 60s. Dr Darby also produced the well-known striped variety Tigerella (a variety which I've seen described around the internet as a poor performer, which has not been my experience of it at all - it would seem that it grows better in the UK than in the US, which has led many American gardeners to be disappointed with it). Anyway, this Pink/Yellow line was never released as a commercial variety, which is a shame, because it is fantastic. The flavour is exquisitely rich and fruity, the texture is just right, the yields are very generous and the rounded fruits are a lovely deep pink-red with yellow stripes ripening to orange. It's definitely one I will grow again, and it has such a lot going for it.

Tangella. Another of Dr Lewis Darby's creations, this bright orange tomato was released commercially and enjoyed some popularity in its day, but was subsequently deleted from the National List and is now rare. Once again, it was the Heritage Seed Library which supplied me with seeds. I don't rate the flavour of this one as highly as the Pink/Yellow variety above; it's milder and mellower, although it does have a tang to it. It is very firm on the outside but has a very soft texture in the flesh, bordering on the mushy when fully ripe. But it is a nice variety, and the colour is absolutely gorgeous ... a vibrant deep orange all the way through and probably high in carotenes. The fruits come out at a variety of sizes and are a rounded apple-shape, and being bred in England, it is very happy with the UK climate.

Tomatito de Jalapa
Tomatito de Jalapa. Another one I'd recommend. This tiddly tiny cherry tomato was given to me by Patrick Wiebe at Bifurcated Carrots, but previously came from Frank Van Keirsbilck in Belgium. The thing that makes it special is that it's supposed to have blight resistance. Others who have tried it have had mixed results, some finding it blight-resistant and others not, with an additional observation that it needs to be deprived of any kind of feed or fertiliser in order to work its anti-fungal magic. My own experience was that it was blight tolerant rather than blight resistant as such. I grew it outdoors with full exposure to the elements, and gave it no fertiliser or special treatment. I also grew a normal non-resistant variety beside it as a 'control' ... not very scientific, but it gave me something to compare it with. Tomatito de Jalapa held off the blight better than the control plant did, and succumbed at a much slower rate, and although it did become infestans-infested, what was interesting was that the blight didn't get into the fruits, even when the stems they were growing on became blighted. Thus the plant was stricken with blight but I was still able to go on harvesting the fruits for some while - unlike the control plant, whose fruits rapidly became inedible. So this is definitely one to try if you want to grow outdoor tomatoes and be fairly confident of getting a crop. Having said that, the blight was a bit later in 2010 than it has been in previous years, so it remains to be seen how it will cope in a "bad" blight season. However, there's more to a variety than disease resistance, and Tomatito de Jalapa has a lot to recommend it. The small fruits are absolutely delicious - sharp and fruity - and borne on long trusses which ripen beautifully in the English outdoors. Productivity certainly didn't suffer much for the lack of fertiliser. So although the tomatoes are tiny, you get a constant supply over a long period, and overall yield is high. I'll certainly grow it again.

Essex Wonder
Essex Wonder. Popular in the 1930s as a market garden variety developed especially for the glasshouse industry in Essex, this is another "deleted" variety rescued from near extinction by the Heritage Seed Library. This crop was grown outdoors, which wasn't really ideal for it, but it coped. I've had better results growing it in a greenhouse in the past. It's a classic tomatoey tomato; in other words it's almost perfectly spherical, bright red, and has a nice old-fashioned tomato flavour. The size varies considerably, as does the thickness of the flesh, and the gel around the seeds is distinctly green.

Anna Russian
Anna Russian. An oxheart-type tomato. Oxhearts tend to be large, strawberry shaped and immensely fleshy, with few seeds. They also tend to be a bit on the bland side, and that's where Anna Russian is a glorious exception, being very rich and flavoursome. The fruits are a deep dark rosy pink with a mildly ribbed surface, and bright red inside. As they're so fleshy (and tasty) they work extremely well in slices and would probably be good in sandwiches. Yields are pretty respectable - higher than you'd think from the rather floppy plants - and early maturing. Despite the name I believe this variety comes from the US, though it may well have been taken there by Russian immigrants. My seeds came from Association Kokopelli in France. Sorry there's no bottle-top for scale in this picture, but the fruits are of quite variable size.

Pink Freud F4
Pink Freud F4. One of my own little projects which I'm quite pleased with. Now in an F4, it produces masses of miniature shiny silky Roma-plum tomatoes on large trusses, dark pink before ripening to deep red. The flavour is fabulous, and they are equally good raw or stewed up into a luxurious sauce. They also have incredible keeping properties, and ripe fruits can be left in the kitchen (unrefrigerated) for weeks on end with no loss of quality. I've no idea who its parents were, it arose from saving and selecting seed from a punnet of F1 hybrid tomatoes I bought in Marks and Spencer's in 2002. A great example of why you should ignore the received wisdom that saving seeds from F1 hybrids is a waste of time. On the contrary, "doesn't come true from seed" is another way of saying "has lots of exciting diversity". So if you grow any F1 hybrid tomatoes, either from seed packets or supermarkets, do try saving their seeds and see what surprising and delightful goodies they throw up for you.

Pugliese Green
Pugliese Green. Perhaps this should be re-christened Pugliese Red. I was given the seeds by Jeremy Cherfas of Agricultural Biodiversity, who is living in Italy and bought the fruits at a local shop. They are thought to be a locally-developed variety from the Puglia region of Italy (the heel of the boot). I grew them in 2009, allowed them to ripen to a full vibrant red, and was absolutely knocked out by how good they tasted. Really one of the best-flavoured tomatoes I've ever tasted. But when I blogged about it last time, Jeremy informed me that this isn't how they are eaten in Italy. As I should have guessed from the fact that he called them Pugliese Green, they are supposed to be eaten while they're still a bit green. So this year I tried it. And yes, they are indeed very tasty while green-ish. But I still maintain that the really knockout flavour develops when they are fully ripe! It's also remarkable how rapidly they ripen. One minute they're sitting there with no more than a blush of red, and the next day when you go to check them they are bright as a post-box. The fruits are medium sized, firm to the touch, and take the form of slightly flattened globes. The photo shows a couple of fruits in the intermediate semi-green stage as well as the full red. Take your pick. The fact remains that this is a very fine tomato, whatever colour it is when you eat it. Thanks Jeremy.

Isis Candy
Isis Candy. Popular in the US but pretty much unknown over here (I bought the seeds a few years ago from an American seed company), this is a little treasure, and actually originated in Eastern Europe. It's a small tomato, but not small enough to call a cherry; it's very rounded and elegantly symmetrical, globe-shaped but distinctly flattened. It's thin-skinned and very juicy, and has a really lovely sharp tangy flavour. It's also very beautiful, passing through many shades of orange, pink and red, sometimes in marbled combination. A regular favourite.

Green Zebra
Green Zebra. A green-when-ripe stripey tomato bred by Tom Wagner in the US and released in the 1980s through his TaterMater seed company. It can now be found in catalogues worldwide, and is widely grown and well loved. Fruits are a decent size and exquisitely striped, with more of a mottled pattern underneath. People often ask how you know when it's ripe, and the answer is that the lighter stripes change to a golden colour, which is quite distinctive when you see it. You can also give the fruits a little squeeze if in doubt. It does taste slightly different from a red tomato, and has quite a sharp, acidic tang.

Banana Legs x Green Tiger F1
Banana Legs x Green Tiger F1. Another of my own breeding projects, this time from a cross I made between one of Tom Wagner's creations, Banana Legs, and a Marks & Spencer's commercial variety, Green Tiger (not to be confused with Green Zebra above). Banana Legs is a light yellow elongated tomato with silvery stripes and a distinct nipple on the end, while Green Tiger is a perfectly spherical, smooth and shiny tomato with deep burgundy red flesh and dark olive-green stripes over its red skin. What I find fascinating about this F1 hybrid is that it's in almost every way an exact intermediary between the two parent types. It's got silvery-green stripes (not very clear in this photo as they stand out more when unripe), and the shape is an extended globe with a small nipple. This half-way blend fascinates me because it's not something that happens in my pea-breeding projects. With peas, the dominant genes assert themselves completely in the F1 hybrid, with recessive traits completely hidden until they start segregating out of the F2. I'm not a tomato breeder, I only have an occasional casual dabble, so it intrigues me to see how differently the genes express themselves in tomatoes. It's results like this which illustrate why it took so many thousands of years for humans to understand the processes of genetic inheritance, assuming wrongly that it was a simple "blending" process, and it also perhaps shows why it was with peas that the great breakthrough of understanding was made. Anyway, I could go on about how beautiful and high yielding this hybrid was, and that the flavour was pretty decent - but it doesn't really matter what traits it has, because I cannot preserve it in this form. Every seed is an F2 with a different genetic shake-up, so presumably when I sow them I will start getting segregation for the various parental traits rather than this half-way mix. But we shall see.

Something else interesting about my 2010 tomato crop which I will only talk about briefly as I need to do some more experimentation before I conclude anything. I took the slightly strange decision not to feed any of my tomato plants, but just to grow them au naturel, as it were. The inspiration for this was an incident in the 2009 season when I became so busy I had to abandon some tomato plants in the greenhouse - only to find months later that they were fruiting beautifully despite having no water or fertiliser, and also in immaculate blight-free health, even though blight was rampaging through the garden outside. This experience set me thinking, and then when Patrick gave me the Tomatito de Jalapa seeds with the instruction not to feed the plants as their blight-resistance only works if they aren't fed, something went ker-chinggg in my head.

So in 2010 I grew my greenhouse tomatoes without any fertiliser whatsoever, and I only watered them when they were really desperate. The results really astonished me. The plants didn't grow anywhere near as big as they would do with a "normal" feeding and watering routine, and so I suppose they produced fewer fruits too, but in terms of the number of fruits which were edible ... the yields were the highest I've ever had. This is because all the fruits were perfect - immaculate, healthy and blemish free. I had no blossom-end rot, I had no splitting (except very late in the season), I had no mouldering and squishing, and most remarkably I HAD NO BLIGHT. There was plenty of blight outside, it killed all the potatoes and the outdoor tomatoes. But the greenhouse tomatoes had none at all. It may be that they were just lucky, or sufficiently sheltered, but I don't think so ... I think they were so happy and healthy they managed to fight off all nasties. It's as if the lack of feeding enabled them to fulfil their natural potential instead of being forcibly plumped up into oversized bloaters. Another possibly significant factor: because the plants only grew to about 6ft and didn't sprawl like triffids all the way up to the ceiling and out the roof, it wasn't necessary to do much pruning at all. I just nipped out a couple of sidebuds when the plants were young and then left them to it. I'm wondering if the non-pruning also helped to keep them healthy, because this is exactly what the great Dominique Guillet asserts in his book The Seeds of Kokopelli. He reckons pruning is nothing short of tomato-abuse, and believes very firmly that the lack of pruning in his tomato crops is what keeps them blight-free.

Lots of food for thought and further experimentation here. If anyone else has any experience with growing tomatoes without fertiliser, or is perhaps brave enough to experiment with it in 2011, I'd love to hear about it.