How to Grow Winter Lettuce in Your Greenhouse

Surprisingly it is feasible, and very easy, to continue growing lettuce throughout Autumn and Winter.

There are several varieties of winter lettuce available which are specifically cold hardy and able to grow in low light conditions.  Winter Density is a compact semi-cos variety with crisp leaves and sweet flavour, Winter Wonderland form large heads with deep green leaves, Valian, which is a popular gem type sweet and crunchy, Merville de Quatre Saison which forms tidy heads with beautiful red leaves. Arctic King and many more.

Winter lettuce can be sown from August to November and with regular planting fortnightly you can ensure a continuous crop till spring, or you can plant more in late Autumn when they will grow faster and just keep picking the outer leaves till spring and the plant will continue to grow.

Seeds can be sown direct into the soil, or for better results you can sow the seeds into seed trays or module trays indoors. Plant them out into beds, as soon as they fill their cells or are at the 2 leaf stage.

Prepare the ground by digging in some organic matter. Plant in a sunny sheltered spot with good drainage, so the plants are not waterlogged. In some warmer parts of Britain, it should be possible to grow lettuce outdoors with no protection, but most gardeners use the addition of a cloche, cold frame, or greenhouse and this has been shown to increase the chances of success. As referenced in our blog “Early lettuce under an Access cloche” we saw there were more leaves on the lettuces grown under glass and the lettuce themselves were significantly bigger compared to lettuces planted at the same time outdoors.

If using a cloche on milder days you can take the cloche off to allow air circulation however with an Access long cloche or salad cloche there is a narrow ventilation slot at the top of each side that allows air movement, and the roof panels can be removed to allow weeding and watering.

To boost yield, if you can grow winter lettuces in a greenhouse, coldframe or polytunnel you will have the most progress, as it is warmer and free from persistent rain and wind.

Growing winter lettuce in a greenhouse can be done in a few ways – particularly the easy-to-grow cut-and-come-again types of loose-leaf lettuce such as winter gem which is perfect for an unheated greenhouse and has good disease resistance. They can be sown into spent grow bags that were used for growing summer-fruiting crops such as tomatoes. Simply fork over the bag’s contents to break up any clods and add some general-purpose potting mix. Plant sturdy plug plants that you have either grown yourself from seed or purchased about six inches (15cm) apart. Give them an initial watering, if you have a misting system this is ideal as it will humidify the lettuces without producing too much moisture, after that you shouldn’t need to water them more than once every two to three weeks. You should be able to pick leaves within about 4 weeks removing just a few outer leaves at a time or with head lettuces like icebergs you can harvest the entire lettuce head.

Winter lettuces are hardy, tenacious, and tasty but by mid spring they will be flowering so at this point dig up to make way for your summer crops.

Searching for more advice on growing vegetables in a greenhouse? We have a wide range of articles to help you grow a variety of vegetables – from growing courgettes to cucumber, sweetcorn to peppers, you’re sure to find enough to keep your greenhouse well-stocked.