How to Grow Lettuce: Varieties, Planting, and Harvest

Choose the right lettuce type

Lettuce falls into four useful groups: loose-leaf, butterhead, romaine and crisphead. Loose-leaf types such as oakleaf are the fastest and easiest, because you harvest outer leaves and the plant simply keeps growing. Butterhead and romaine form hearts but still shrug off light frost, while crisphead (iceberg) needs a long, cool season and rarely succeeds in hot climates. If your summers are warm, look for bolt-resistant names such as Jericho, Nevada and Muir.

Time it as a cool-season crop

Lettuce germinates best when the soil is between 15 and 20°C, and it turns bitter and bolts once days climb past 25°C. Sow directly in early spring, roughly two to four weeks before your last frost, then sow again in late summer for an autumn crop. In hot regions grow it as a winter crop, or give the bed afternoon shade. The most common mistake is sowing too late in spring and watching the plants race to flower before they size up.

Sow shallow and thin hard

Lettuce seed needs light to germinate, so cover it with no more than 3 mm of soil and press it gently onto the surface. Keep the bed damp with a light daily mist until seedlings appear in 7 to 14 days. Thin loose-leaf types to 15 cm apart and hearting types to 25-30 cm, because crowded lettuce stays small and mildews quickly. Eat the thinnings — they are tender, sweet and perfect for a salad.

Water, feed and mulch

Lettuce has shallow roots and dries out fast, so water little and often rather than flooding once a week. Mulch with straw or compost to hold moisture and keep the leaves clean of splashed soil. Feed lightly with a nitrogen-rich organic fertiliser every three weeks; a heavy dose at once produces soft, brittle leaves. Steady moisture is what keeps lettuce crisp instead of bitter.

Harvest for a long season

For loose-leaf and butterhead, either cut the whole head 2 cm above the crown or pick outer leaves one at a time so the plant regrows for several rounds. Harvest in the cool of the morning and plunge the leaves into cold water to keep them crisp. Sow a short row every two to three weeks and you can cut fresh lettuce from spring right through to autumn.

Slugs, aphids and bolting

Slugs are lettuce's main enemy: set beer traps, water in the morning and clear away damp hiding places. Aphids cluster in the heart of the plant, where a sharp jet of water usually dislodges them. If a plant suddenly shoots upward and tastes bitter it has bolted, so pull it and sow again rather than trying to rescue it.

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