If you can keep the slugs off them, lettuces are one of the easiest edible plants you can grow for seed saving. But because they turn bitter once they decide to flower, most of us never give them the chance: as soon as they start to stretch upwards, we pull them out. Which is a shame really, because if you just leave them alone they’ll give you seeds to grow next year.
If you’ve not saved seeds before lettuces are a great place to start, but we recommend you read our saving pea seeds article to understand some of the points we’ll be making a little better. Such as, you can’t save seed from F1 varieties… so don’t bother trying!
To get a bit of genetic variety you’ll need to select about three strong plants for seed saving. They’ll be in the ground quite a bit longer than regular lettuces, and they’ll get fairly tall (between 1 and 2 metres for some varieties) so you need to plan ahead to make sure you have room for them.
When you grow a batch of lettuces, choose five or six of the stronger seedlings to leave to grow undisturbed, with no picking except to remove dead leaves from the outside. When they finally bolt, be ready to support the central stem with a cane if needed. Without support, many lettuces will be blown over by the wind or just collapse under their own weight. ‘Heading’ varieties may need a little help too, as the tight heads so favoured by supermarkets sometimes fail to open properly. If you see an unhappy looking bulge in a heading lettuce, gently cut a cross through the outer leaves with a sharp knife and the central stem should emerge a few days later.
Once bolting has begun in earnest, remove any of the plants that look in any way odd. It’s also a good idea to remove any early bolters, so that you’re left with the strongest and latest two or three plants. Selecting in this way means that next year’s plants should be more vigorous, but not so quick to turn bitter as they grow.
The central stem of the lettuces will soon bear hundreds of tiny dandelion-like flowers, which die back and are replaced about a fortnight later by dandelion-like tufts of feathery down. For the best yields these can be plucked from the plant daily, with the little seeds attached at the base – but this takes a lot of time. Only seeds from the first flush of flowers should be collected, as they’ll be the most vigorous.
For faster seed collection, wait until the first flush of seeds are ready to collect, then cut the whole thing off at ground level. Gently gather the top growth of the plant together and stand it upside down in a clean bucket, and put it somewhere dry and cool. This encourages it to open as many seed pods as it can. A few days later, give the whole plant a shake over the bucket and then pluck or rub off as many seed heads as you can. You can either do this over the bucket, or over a piece of sheeting for speed. Either way, you’ll soon end up with a mixture of seeds and other unwanted material collectively termed chaff.
Rub the mixture of seeds and chaff fairly firmly to break it up a bit (an old pillowcase makes this easy). To separate out the seed from the chaff, put a handful of the mixture into an ordinary kitchen sieve and shake it over a saucepan. Some seed will fall through, but most of it will puddle at the bottom of the sieve leaving the chaff to rise to the top. Pick pinches of chaff off with your fingers and put them in another pan, give the sieve another shake, and repeat until the seed is reasonably clean. You don’t have to be obsessive about it – you’re not trying to produce professional-looking seed here. A few bits of chaff won’t affect storage or germination, so stop as soon as you reckon it’s clean enough to sow.
Most of the time you’ll have so much seed you won’t know what to do with it all. However, if you didn’t get as much as you’d hoped, give the ‘spent’ chaff another rub and repeat the sieving process to collect any seeds you missed.
Lettuce seeds are so small that they need little extra drying, but a day or two spread out in a single layer somewhere cool and dry is still a good idea. The seeds will remain viable for up to five years if stored in a zip-lock bag in a cool dry place. Make sure you label it with the variety and date.
Other seed saving articles (more to follow shortly)