Sweet peas Lathyrus odoratus. Photograph: Julie Pigula /Alamy
It has been one of those effortless sweet pea years. Every plant romped away, the mildew never appeared and even if you were beaten by the endless picking, they continued to flower. A wet winter, then a hot, dry summer is sweat pea perfection.
Will it be the same next year? Who knows with our variable climate; still, some old tricks work well whatever the weather. If you have somewhere sheltered, not necessarily always frost-free, but away from the worst of the weather, an autumn sowing of sweet peas is worthwhile. Six months of growing now means sturdy plants come spring. Take your favourite sweet pea, chosen for shade or perfume (I suggest getting lost in the catalogues of Chiltern Seeds, Easton Walled Gardens and Roger Parsons). Sow in a deep pot, such as a long tom or a root trainer, in peat-free multipurpose compost. If your compost doesn’t come with food (and most do), add some slow-release fertiliser, such as seaweed and chicken manure pellets.
In the middle of each pot, press in a seed a couple of centimetres deep and cover with compost. Water in the seeds (or sit the pots in a shallow tray of water until the top is wet), then place somewhere sheltered but cold. An unheated greenhouse, a porch with good light, a cold frame, even an old fishmonger’s box will work. The trick is to keep water off the plants to prevent rotting.
If you grow them somewhere too warm, you end up with a tangled mess of growth that becomes slug fodder and will turn to black mush if hit by a surprise hard frost. If you get too much top growth, pinch back to two or three sets of leaves and put them somewhere cooler. However, if you’ve had them on what you thought was a cool windowsill, I wouldn’t abandon them to somewhere too cool, too quickly; you’ll have to ease them into their new conditions. Fleece is your friend here.
What you’re aiming for over the winter is very slow top growth and lots of happy roots below. Get the temperature right (nothing below -5C) and offer as much light as you can, and that’s about it, other than remembering to water them every so often. After a winter of this regime, you’ll have tough plants that need little mollycoddling the following spring. Once the worst frosts are over and the soil is warm (all the weeds will start germinating as an indicator), plant them out into rich soil and away they will romp.
The only downfall to this method is mice. Sweet pea seeds seem to release some inner mouse passion, like us hunting for truffles in autumn. Poison isn’t exactly fair game, so aim to deter them instead. A pane of glass over the pots until the first leaves appear works well, as does any fine mesh. Or try suspending the seedlings on raised boards, say from polytunnel hoops.
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