Lettuce

Lactuca sativa

With loose-leaf lettuce you pick a few leaves at a time for weeks. Hearting kinds are cut whole once the heart is firm. Lettuce grows fast in cool weather but runs to seed when it's hot. So sow a short row every two to three weeks, not all at once.

Looking after it

Water: Lettuce needs a lot of water, so keep the soil moist all the time. In a dry spell the leaves turn bitter and the plants bolt, shooting up a flower stem. Water in the morning, not the evening, to keep slugs and mould down. Feeding: It needs little food. If compost went in before sowing, plants in the ground need no feeding. In a pot, give a general liquid feed every two weeks in summer.

Harvest and keeping

On loose-leaf types, pick the outer leaves once they are about 10 cm long. Or cut the whole plant down to a 2.5 cm stump and let it grow back. Cut hearting types at the base once the heart feels firm. Pick in the morning, when the leaves are crisp. Eat butterhead lettuces soon. Crisphead types keep longer in a bag in the fridge.

What can go wrong

Slugs and snails. You find ragged holes and slime trails, worst on seedlings in damp weather. Pick the slugs and snails off at dusk and water in the morning.
Bolting. After heat or dry soil, a tall flower stem shoots up from the centre and the leaves turn bitter. Water regularly and sow summer lettuce in light shade. Pick the plants before they get old.
Downy mildew. In cool, damp weather, angular yellow patches appear on top of the leaves with white fuzz underneath. Space the plants so air can move and water the soil, not the leaves. Pick off the affected leaves.

Growing facts: RHS, UC ANR and seed-company sowing guides. Lettuce care: RHS. How many to grow: University of Missouri and Kansas State extension. pH: Washington State University extension.