Lettuces are easy to grow and come in a wide range of colours, flavours and textures – your salads need never be boring! There are two main types – hearting lettuces have a dense centre, while loose-leaf lettuces have open leaves and no heart. You can also grow various mixes of salad leaves to be picked while young and tender.
Jobs to do now
- Thin seedlings as necessary
- Keep sowing little and often, for a regular supply
- Protect from birds, by covering with fleece
Month by month
What to sow
When buying seeds, there is a huge diversity to choose from.
Hearting lettuces, which come in three main types:
Butterhead lettuces have an open shape, are quick-maturing and tolerate poorer growing conditions
Cos types have an upright, oblong head
Crisphead types produce large hearts of curled, crisp leaves and are more resistant to bolting (going to seed prematurely). This group includes iceberg lettuces
Loose-leaf lettuces and salad-leaf mixes produce less dense growth, ideal for picking individual leaves and for growing in small spaces and containers. Choose from a range of colours, flavours and leaf shapes.
How and when to sow
Grow lettuces in full sun in moisture-retentive soil. Early and late sowings may need protection against cold, using cloches, plastic tunnels or horticultural fleece.
You can also grow lettuces in containers and growing bags, but be sure to water regularly.
Sow seeds thinly, 13mm (½in) deep, in rows 30cm (1ft) apart. Sow a short row every fortnight to ensure continuity of cropping.
When to sow depends on when you want the harvest:
For summer/autumn cropping: sow outdoors from late March to late July. For an even earlier crop, sow indoors in early February in seed trays and plant out in early March under cloches or plastic tunnels
For early winter cropping: sow outdoors in early August and cover plants with closed cloches from late September onwards
For spring cropping: sow a cultivar such as ‘Winter Density’ in September/October, either in an unheated greenhouse or in mild areas under cloches or in a coldframe.
When sowing in summer, bear in mind that high soil temperatures can prevent some cultivars from germinating. So in hot spells, sow in the evening, water with cold water and provide some shade to keep temperatures down.
Thin seedlings as soon as the first true leaves appear and continue until the plants are 30cm (1ft) apart. The seedlings you thin out can be added to salads.
Water when the soil is dry, ideally early in the morning.
Early in the year, sparrows can be a problem as they find young lettuce plants irresistible. Protect with fleece, chicken wire or similar. Also protect plants from slugs and snails – see Common problems below.
You can harvest lettuces from late spring through to winter, if sown regularly using suitable seasonal varieties.
Whole lettuces are ready to harvest when a firm heart has formed – cut through the stem at the base.
Loose-leaf varieties can be harvested as soon as the leaves are big enough to be worth eating – either snipping a few outer leaves from each plant or cutting the whole lot from one plant.
Lettuce — butterhead
Lettuce — cos
Lettuce — crisphead
Lettuce — loose leaf
Lettuce root aphids
These pests can cause older plants to suddenly wilt and die back, usually in mid- to late sunmmer. You may not see the aphids, as they feed on the roots, not the leaves, but you may see lots of ants around the plants, as they feed on the honeydew that the aphids produce.
The damage is worse in dry conditions, so keep lettuces well watered. If you suspect root aphids and only have a few lettuces, you can carefully dig them up, wash off the aphids and replant in fresh compost. Otherwise, there’s not much you can do, except pull up and destroy affected plants. Prevention is the best cure, so cover lettuces with insect-proof mesh (such as Enviromesh) from June until August, as this will prevent aphids getting to the roots. Some lettuces are resistant to root aphids.
Slugs and snails
These feed on the young seedlings and you'll see the tell tale slime trail on the soil around your crop, as well as on the leaves.
There are many ways to control slugs and snails, including beer traps, sawdust or eggshell barriers, copper tape and biocontrols.
A usually grey, fuzzy fungal growth which can begin as pale or discoloured patches. Grey mould ( botrytis) is a common disease especially in damp or humid conditions. Spores enter plants via damaged tissue, wounds or open flowers. Mould can also damage ripening fruit such as strawberries. Black resting spores survive over winter.
Remove damaged plant parts before they can become infected. Cut out infected areas into healthy tissue and clear up infected debris. In greenhouses, reduce humidity by ventilating and avoid overcrowding of young plants and seedlings.
Plants flower and set seed prematurely.
Unless growing for seed sow bolt-resistant varieties. Sow or plant at the correct time and keep the soil or compost moist.
The Royal Horticultural Society is the UK’s leading gardening charity. We aim to enrich everyone’s life through plants, and make the UK a greener and more beautiful place.