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Lettuce

From seed to salad bowl in about six weeks, and cut-and-come-again types give you four harvests from one sowing.

1. Sow a short row every two or three weeks instead of one long row, so you are not swamped.
2. Sow 5 to 10 mm deep in damp soil, thinly, in rows 30 cm apart.
3. In hot weather sow in the evening, because lettuce seed refuses to germinate above about 25 C.
4. Thin to 15 cm for loose leaf or 25 to 30 cm for hearting types, and eat the thinnings.
5. Water in the morning at the base so the leaves are dry by evening, which cuts slug damage.
6. Shade the bed with mesh or a taller crop from May onwards in hot climates.
7. Cut loose-leaf types 3 cm above the crown and they regrow for another two or three cuts.
8. Pull hearting types whole once the heart feels firm, before a flower stalk forms.

Soil

Moisture-retentive, fertile soil at pH 6 to 7 with plenty of compost worked in.

Sun

Full sun in spring and autumn, light afternoon shade in summer. In Portugal, summer sun alone will bolt it.

Water

Little and often. Lettuce is over 90 percent water with shallow roots, so it needs damp soil constantly, roughly 15 litres per square metre per week, best given in the morning.

Spacing

Loose leaf 15 cm apart, hearting types 25 to 30 cm apart, rows 30 cm

Depth

5 to 10 mm deep, very shallow

Care

['Keep the soil damp at all times. A dry check makes leaves bitter and triggers bolting.', 'Slug patrol in the first three weeks decides whether you get a crop at all.', 'Feed lightly once with a nitrogen-rich liquid feed if the leaves look pale.', 'Weed carefully by hand, because the shallow roots damage easily with a hoe.', 'Sow bolt-resistant or cos varieties for the warm end of the season.']

Harvesting

Pick outer leaves from the outside in and the plant keeps going for weeks. For cut-and-come-again, take the whole clump down to 3 cm with scissors. Harvest early in the morning when the leaves are full of water and crisp.

Storing

Lettuce does not store. Wash, spin or pat dry, and keep in a sealed box lined with a tea towel in the fridge for up to a week. It cannot be frozen or dried usefully, so plan successional sowings instead of trying to preserve it.

Grow it next to

Good with carrots, radish, beetroot, onions and strawberries, and happy in the shade of taller beans or sweetcorn in summer. Keep away from parsley, which runs to seed and shades it out.

Problems

[{'cause': 'Bolting from heat, long days or a dry check', 'fix': 'Sow in spring and autumn only in hot climates, keep soil damp, use bolt-resistant varieties, and give afternoon shade. Bolted plants are not worth eating.', 'symptom': 'A tall flower stem shoots up and the leaves turn bitter and milky'}, {'cause': 'Slugs and snails, which favour young lettuce above almost anything', 'fix': 'Water in the morning, clear hiding places, go out with a torch after dark for two weeks, and use wool pellets or a beer trap. Transplanting larger modules beats direct sowing here.', 'symptom': 'Seedlings vanish overnight leaving only stumps'}, {'cause': 'Downy mildew in cool damp crowded conditions', 'fix': 'Space wider, water at the base in the morning, remove affected leaves, and rotate the bed.', 'symptom': 'Pale yellow patches on top of leaves with grey mould beneath'}, {'cause': 'Aphids, often protected from predators inside the folded leaves', 'fix': 'Hose off, or spray with a soft soap solution. Grow open loose-leaf types if this keeps happening, and encourage ladybirds and hoverflies with flowers nearby.', 'symptom': 'Colonies of green or grey aphids in the heart'}, {'cause': 'Thermal dormancy above about 25 C of soil temperature', 'fix': 'Sow in the evening, water the drill with cool water, and shade the row. Or start in modules somewhere cooler and transplant.', 'symptom': 'Seed sown in midsummer simply never comes up'}]

Saving your own seed

Very easy. Lettuce self-pollinates so varieties rarely cross, though 3 m of separation is sensible. Let one good plant bolt and flower, then collect the fluffy seed heads over several days as they ripen unevenly.

Containers

One of the best container crops. A 15 cm deep trough or even a window box works. Loose-leaf mixes sown thickly and cut with scissors suit pots better than hearting types.