I'm going to grow some sweet peas from seed and it's the middle of December which is a really good time to do it. We've done lots of experiments here at Perch Hill and we had begun to think that January is fine and even February, but this year (the last season) we sowed them earlier about this time and we saw huge benefits; the plants were stronger, they had stronger roots, better disease resistance, they didn't get mildew and they produced more flowers. I definitely think it's worth it, so if you can do it this side of Christmas or early in the New Year.
Sweet Pea Rootrainers
I’m going to sow my favourite sweet pea of all, which is called ‘Prince Edward of York’ and I'm going to use rootrainers. Here’s how they work, they are truly brilliant for sweet peas! You get a pack of these cells and each cell has a long, thin profile so it's like a loo roll, also the cell has channels down the side which is equally important. The reason for the long, thin shape is that a legume like a sweet pea or a broad bean germinates by putting out two shoots, one goes up and the other goes down. The one that goes up continues to grow and the one that goes down grows more quickly and when it gets to the bottom of the cell it breaks off, then it branches out all the way up the rootrainer. That’s why a loo roll or rootrainer is ideal because you’ve got a longer tap root before it breaks off compared to a short pot. You then end up with more lateral root formation all the way down the length of that rootrainer.
The advantage of a rootrainer over a loo roll is because of the channels, when the lateral roots get to the edge of the pot, it’s guided straight down to the bottom of the cell rather than going round and round as if in a loo roll. Those lateral roots then create more lateral roots, forming a root ball much quicker.
I’m filling this rootrainer with a non-peat based multi-purpose potting compost, I check I have enough compost to the right depth so I can start to put my seeds in, two seeds to each cell. The compost should be about an inch deep at this stage. The reason I sow two seeds to each cell is because in a domestic garden you don’t want to grow cordon sweet peas where you have to pinch out every single side shoot, you just get one momentous trunk growing up a cane, and you will get fewer flowers but longer stems. This is extremely time consuming which is why we plant two seeds to every cell, the seedlings then stay as a couple all the way through their life. So when I’m ready to plant these out I unclip the cell and have my pair of sweet peas, they are then planted into the ground as a pair. I don’t tear the roots apart as sweet peas don’t like that, and they’re planted in the ground at the base of a cane.
Start to back fill the cells with more compost over the top. Water them with a fine rose (turn the rose upside down so you get a finer spray from your watering can). I’ve sown one variety and now I’ll sow the rest of this rootrainer with ‘Matucana’ which is my second favourite sweet pea.
Planting Out Sweet Peas
I’m going to put these in a cold frame or on a bench in a shed, then label them. I’ll come back and look at them in two weeks time, when hopefully they will have started to germinate and if they do I’ll keep an eye on them. Once they start to grow to two-three inches tall, I’ll pinch out the tips which will produce a bushier plant. Then, when the roots are coming out of the bottom of the cell I’ll pot them up into a bigger sweet pea container and plant out in the garden in mid-March.
One last thing, mice love sweet peas so be sure to protect them otherwise they’ll eat the lot!