Lettuce is one of the best plants for polytunnel growing. A polytunnel can make the process of growing lettuce easier as you can more easily control the environment and prevent slugs or other pests from eating your crop. Lettuce comes in a wide range of different varieties, hearted or loose leaf. Cut and come again varieties provide a quick crop for endless summer salads. Lettuce can be planted in the ground in your polytunnel, in containers or even in vertical gardens or baskets hanging from the crop bars. Since it can be grown in small spaces, lettuce can help you make the most of the space in your polytunnel.
While lettuce will like a sunny spot in the spring, by the time summer rolls around, the sun may be too fierce and many types of lettuce can be prone to bolting and going to seed. To minimise the risk of lettuces going to seed, you can sow it in the shade of other, taller plants. Lettuce can be sown almost all year round. There are types that are best suited to summer growing and others that will happily overwinter with just a little protection. Sow lettuce little and often to get a continuous crop – sow seeds thinly every couple of weeks to make sure you have a steady supply. It is worthwhile noting that if you let some lettuce go to seed, it is easy enough to collect for next year. If you do not then you will have to buy new lettuce seed each year as it does not remain viable seed for long.
For hearted lettuces, you will have to make sure that you thin seedlings as soon as the first true leaves appear. (You can eat thinned lettuces as a micro salad.) Continue to thin hearted lettuces until they are around 20cm apart. Some loose leaf lettuces should also be thinned to around this spacing, though for cut and come again varieties, spacing is not as important as long as there is enough nutirition in the soil or planting medium and the plants are provided with enough water. Try to water roots and not leaves and water only in the morning.
Winter salads will have to be given extra protection of fleece, cloches or similar even inside the polytunnel in most parts of the UK. Cloches can be made from plastic drinks bottles and can also be used to sow lettuce earlier in the spring.
Cut and come again varieties can be ready in as few as six weeks and you can keep picking individual leaves from the plants. Hearted lettuces will require a longer growing period and should be cut whole. If you choose the right varieties then you can be enjoying fresh salads from your polytunnel all year round.
Sow under cover in February and March
Expecting cutting – May to October
Spring crop (only in mild parts of the country):
Sow under cover between August to September
Expecting cutting – April to May