The cool spring has been great for getting salad leaves going in the greenhouse, lettuce in particular. Most plants are in the greenhouse now to keep them warm while the weather is still uncertain – I even have new perennials sheltering in there as it has been so chilly and I haven’t wanted to plunge them out into the cold – but lettuce doesn’t mind the cold. In fact, in a hot summer it can be really tricky to get enough lettuce sown at all. Germination rates drop during hot weather, and so a generous sowing can leave you with just a few seedlings. Not so now. The greenhouse is providing just the right amount of shelter but also the temperatures are low, and thought I didn’t count the seeds going into the seed tray, it certainly seemed as if every one of them germinated. We have been left with loads, and have pricked a clump of them out into small pots, which will then be planted out spaced apart and able to grow into heads of lettuce while the rest we have left in the seed tray, and will soon start cutting and eating as a cut-and-come-again crop of tiny baby leaves. As long as they are kept watered they can be cut up to three times and left to grow again before they wear themselves out and need a tray of replacements sown.
Those individual lettuce plants are destined to be planted in among our broad beans, which we are inexplicably having the best success with this year. Broad beans seem to be entirely hit and miss depending on…well who knows what? Weather conditions, the phase of the moon, the whims of the legume gods? We have tried sowing them in autumn and they have been hit by hard winter weather, and tried sowing them in early spring and they have grown up tiny and mean, producing three pods per plant. These ones were sown in February, direct into the ground, and they have grown up beefy and perfect. They will provide the perfect shade for lettuces to nestle under.
Lettuces are brilliant catch crops, which means a crop that can be squeezed into the spaces between another crop. It doesn’t have much of a footprint itself and needs little from the soil, so doesn’t compete, but it loves the cool shade cast by other plants and will also spread out and prevent weed seedlings from germinating. A very good companion for my broad beans.
If you do want to sow shade-loving lettuces later in the year when the weather is hot, there are a couple of tricks you can use. It helps first to know that there is a period about three hours after sowing during which temperature is crucial to germination success. If it is nice and cool you will get plenty of seedlings, but if it is hot then you will get very few. You can use this knowledge to your advantage by sowing right at the end of the day. It doesn’t matter how hot it is when you sow, but how hot it will be in three hours’ time, so if you can sow at say 6pm on a summer evening, the crucial moment will come at around 9pm. By then the temperature will hopefully have dropped significantly and germination will be good. You can cheat further of course by mixing seeds with compost and a little water and putting them into the fridge overnight, and then scattering this across a seed tray the next morning. But for now, we have the perfect weather for lettuce, no tricks required. Right now it is very easy to grow yourself as many soft sweet lettuce leaves as you can eat.