Pink flowered pea update – the F3 generation

The climate in the UK is bonkers at the moment. Within the last fortnight we had a frost which had me scrabbling to protect all my tender plants. Now we have a record-breaking heatwave, with temperatures well over 30° … extreme and abnormal for May. Aside from being an alarming sign of how the climate emergency is accelerating, for my pink-flowered pea project it couldn't have come at a worse time.

Peas are a cool season crop. They can't deal with intense heat from the sun. If temperatures are too high, they struggle to flower and set pods. If they're exposed to full-on hot sun, their delicately watery leaves just dry up and shrivel. Normally the British spring weather is ideal for them, but this year they have been hit by conditions they can't deal with, right at the time they started flowering!

Above is the very first flower from this batch, which opened the day before the heatwave hit.

24 hours later, many of the plants looked like this:

Yes, that is a flowering top full of newly formed buds, dried out and burned to a crisp.

Damage like this is woeful for any gardener trying to get a crop of peas, but when it's a breeding project where the seeds are irreplaceable, it's potentially calamitous. I sowed almost all of the seeds I had available, so if this crop doesn't produce seed then I'm stuffed.

I do still have a couple of spare metres of Thermacrop fabric, so I chucked that over the top of the pea frame to screen a little of the sunlight off the plants. And it seems to be working. Thermacrop is designed to do the opposite of this, keeping plants warm. But in this instance it seems to work for keeping them cool, giving them dappled sunlight rather than an intense blast, and allowing air flow through so the heat doesn't build up underneath. Many plants are already damaged but this is at least stopping it from getting any worse.

The damaged plants are gamely still opening their blossoms where they can, and those which are more severely affected should be able to produce new shoots and have another go. So fingers crossed this is a setback rather than a disaster.

Let's have a recap on this project. It started way back in 2007 when I made a cross between Alderman, my favourite tall white-flowered garden pea with outstanding flavour, and a strange little pink-flowered umbellatum-type pea which came from the Heritage Seed Library under the generic name Salmon Flowered, but which resembles a Swedish heirloom called Rosakrone. Umbellatum or crown peas, once thought to be a different species because they look so different, are the result of a combination of recessive genes which cause fasciation, or stem-thickening, leading to all the flowers and pods being produced together in a clump at the top. Now very rare, they used to be popular in the 17th century before modern pea types superseded them. The aim of this project is to create something with all the garden and culinary qualities of Alderman, but with those beautiful pink blossoms.

For various reasons it took until 2019 for me to grow out the F2 seeds from this project (see this post for the write-up) but it was broadly successful and from 16 plants I got 4 plants with the recessive pink flower trait – a perfect Mendelian ratio, no less. One of them was lost to a weather-related accident, but the other three produced seeds for the F3 generation. And those were what I sowed this year.

Here they are, newly sprouted back in March.

Ignore for now the two rows on the right hand side. These are growing alongside the others but are from a separate project, a cross between Sugar Snap and Salmon Flowered which are still at the F2 stage and will be covered in a separate post. The four rows on the left are what we're talking about here. 

The first two rows are seeds from a plant numbered ASF 06, which was the best of the F2 plants in 2019. This plant produced seeds with a lot of diversity, including some which were wrinkled and some which were smoother with dimples. I've sowed one row of each, marked with W for wrinkled and D for dimpled. I thought it would be interesting to sow these separately, since wrinkled seeds are associated with higher sugar content and sweeter flavour. 16 seeds altogether from this parent plant, of which 15 germinated. Next we have 8 seeds from plant ASF 03, and 8 from ASF 15. These all germinated, so that gives me a total of 31 plants for my F3 generation. I'm pretty chuffed that most of them did germinate, given that the seeds had been left in a box for seven years.

Fast forward two months, and all of the above plants are starting to flower. There are some which are earlier than others, but there's only really a few days between them, so the flowering times are showing more uniformity than they did at the F2 stage.

Now, this project potentially has two recessive traits which I would like to get rid of. One is the umbellatum trait which has all the flowers clustering in a single bunch. I really don't want this, because it reduces yield and makes the plants top heavy and liable to fall over. The other is the gene which causes white flowers. As regular readers will know, there isn't a gene for white flowers as such, there's simply a gene which switches off all pigment production in the plant, of which white flowers are the consequence. This too I need to eliminate, because the whole point is to have pink flowers. If I'd been really lucky, I might have found one or more of these breeding lines not carrying either of the unwanted recessives. Sadly, both traits are indeed showing up in the F3 crop. Arse.

The umbellatum clump-top trait is complicated, and to the best of my knowledge involves three recessive genes. I don't know much about how they work, or whether all three of them are needed in order for the umbellatum trait to be expressed. Maybe they will only have two and will express partially, or maybe all three genes are lurking in the genome and will randomly appear in subsequent generations on the occasions when all three align. That scenario would make the umbellatum types relatively rare, but make it hard to eliminate them altogether. In this F3 crop only one plant is expressing it, and that's one of the offspring from ASF 03.

It is very pretty, and the flowers are pink, but this one unfortunately won't be contributing further to the Pink Flower project, because we don't want any more of these recessive genes thank you very much.

The white flower gene is much more straightforward. One recessive gene, with one simple function. Easy to spot and easy to weed out. Except that in the F3 plants so far, it's not inheriting in quite the way I expected.

It's still early days and not everything is in flower yet, but the presence or absence of a pink splodge in the leaf axils is a reliable indication of flower colour, so I'm able to predict what the colours will be. All three of the F3 breeding lines are producing some white flowers, so obviously all three of them have this unwanted recessive. Given the simplicity of the gene and past experience of working with it, I would expect an average of one in four of these plants to have white flowers. But the ratios are looking like this.

ASF 06 – 7 pinks and 8 whites

ASF 03 – 6 pinks and 2 whites

ASF 15 – 4 pinks and 4 whites

Hmm. We have a normal Mendelian ratio on ASF 03, but the others are looking more 50/50 pinks and whites.

A couple of caveats. One is that they aren't all in flower yet, and it's always possible that I've misidentified the colours until I actually see them bloom. The other is that this is a very small sample size and they won't necessarily make the expected ratios in such a small quantity of plants. This is probably the most likely explanation, i.e. it's nothing more than luck of the draw that I've ended up with fewer pinks than anticipated.

It's a minor frustration inherent in plant breeding. But on the plus side, I get to eat the white ones. Nom nom.

As I said, it's early days with this crop, and I now have the fun (but hard work) bit to look forward to: making notes and observations on every individual plant as they develop. I am pleased to say that nearly all the plants are showing good vigour and have grown to 5 or 6ft tall. This might be hybrid vigour from the cross of two very diverse original parents, or it might just be that they've all inherited the gene for tallness, which is dominant.

The plant which is looking to be the most interesting so far is ASF 06 / 01. Very vigorous and strong, it has lovely big pink splodges in the leaf axils and is also producing very developed sideshoots. It's too early to say whether the sideshoots will develop fully and actually produce flowers and pods, which is a relatively rare thing in peas, but they do look as though they might. This plant is also at the moment showing a very intriguing flower colour. Instead of the two-tone pink which others have, this one has a more uniform apricot pink which I've never seen before. I was quite excited when it first appeared, but knowing how environmental factors can impact the pigments in pea flowers, it may well just be a byproduct of the heat damage. As you can see in the photos below, this plant did suffer a bit while the buds were forming and so this colour may not be representative!

On the other hand, if the flowers do stay this colour I will be well chuffed! I've never seen this apricot shade in peas before, and it's lovely.

Finally, I built a decent pea frame

Look at this magnificent specimen. Well, it's magnificent by my standards. Despite my long term pea passion, this is the first time I've had a purpose-designed pea frame, and I thought my breeding projects probably deserved it by now. It's made from aluminium tubing with jute netting, and it's very sturdy (purchased from Gardening Naturally in Swindon). I even splashed out on some Thermacrop to wrap round it, a type of horticultural fleece which is normally used to keep plants warm but in this instance is for keeping the wind off. Peas aren't too bothered by the cold but they get traumatised by the blustery squally winds which are part and parcel of our spring weather in the UK. The way things are going, it might also come in handy for shading the plants from the full force of the sun.

The new frame (frames, actually, because I bought two) has been brilliant so far. I can fit two whole seedtrays of peas in it because it's so spacious, so it's now planted up with both red podded mangetout peas and pink-flowered peas – two breeding projects in one frame.

Just to give some context, I used to do it like this.

This contraption (from 2009) was made from some of the reams of net curtain which I removed from the windows of my house when I first moved in, plus some bamboo sticks painstakingly lashed together with string. It may look as if Miss Havisham's bloomers blew off the washing line but it was actually extremely effective at doing what it needed to do, which was to give targeted wind protection without losing too much sunlight. So I would absolutely advocate doing it this way if you're on a budget and have a heap of unwanted net curtains available.

But it's labour-intensive to cobble together a shoddy frame like this, and it seldom survives more than a season without needing to be redone. It's too small-scale to hold a lot of plants and sometimes needs emergency reinforcement when their weight gets too much for it. The net curtains work fine but Thermacrop does a better job, because it's got a very open weave which lets the wind move freely through without buffeting the plants. Thermacrop doesn't cost much anyway, so it was well worth the upgrade.

To prepare for the new frame, I dug over a small patch in a sheltered corner where the soil is really good, because I've dumped loads of horse poo on it over the last couple of years. When I say dug, I should explain that my methods have changed a bit in recent times. I now work on the basis of doing as little digging as possible, and I've also discovered a medieval-style field hoe which has been a gamechanger in backache-free tilling. I use it just to very gently cultivate the top couple of inches of soil, leaving the deeper levels untouched. I don't dig with a spade any more unless I really have to. The worms and microbes do a fab job of maintaining the deep soil structure without any need for my intervention.

So here we are with the basic layout. Forty minutes of swearing later, I had this:

The swearing is no reflection on the product itself, which is excellent. It's just that I was putting it together on my own, and it is definitely easier as a two-person job, just because you need someone to hold one end up at the right height while you put it together. I had to resort to propping it up on the back of the bench. You're also supposed to use a mallet to bang the bits together, but I didn't have one, so I had to make do with a metal claw hammer with a sliver of wood under it, which was suboptimal.

And then it was just a case of adding the jute netting, and getting the building inspectors to come and check it out and make sure I'd done a proper job.

The inspectors agreed that yes, this is absolutely the best cat lavatory they've seen in the garden this year.

And in go the peas! 

My Alderman x Salmon Flowered F3 hybrids went in first, and then a couple of weeks later were joined by the red-podded mangetout project, which is now in an F5 and hopefully starting to be properly stabilised (I bloody hope so anyway).

Even though the frame has netting for the peas to climb up, I still put a load of twiggy sticks in there. The main purpose of this is to keep the young plants off the ground, as they tend to flop and that makes them vulnerable to slugs and snails. The twigs hold them up and also give their little tendrils something to grab hold of to help get them started. I put small twigs in among the newly planted plants and then a row of taller sticks down the middle of the bed, which will give them some extra support at a later stage. (It needs to be done now, because it's really hard to add them later without damaging the plants.)

I also added the Thermacrop curtains, which fitted beautifully around the frame and was just long enough to meet in the middle, keeping it all fully enclosed to stop the cats from getting in there.

As you can see, that's going well.

I'm really pleased I invested in these frames though. They are well made and should last years. I've now built the second one (this time with the help of my music partner, Marvin) and that's now been planted up with my F5 purple-podded mangetout peas plus a few satellite projects derived from my red-podded projects. So there's plenty to look forward to.