How To Grow Lettuce / RHS Gardening

Lettuce seeds can be sown indoors or outdoors, in containers or in the ground, from spring through to autumn. Lettuce plants, especially loose-leaf varieties, take up very little space, so are handy for filling any small gaps on the veg plot. They can also be sown between slower-growing crops, such as parsnipsandsweetcorn, as they will be harvested before the main crop needs the space.

When to sow

This depends on when you want to harvest:

• For summer and autumn harvests: sow outdoors from late March to late July. For an even earlier crop, sow indoors in early February and plant out in early March undercloches
• For early winter harvests: sow outdoors in early August and cover plants with cloches from late September onwards. Alternatively, grow in a greenhouse border or container
• For spring harvests: sow a winter variety such as ‘Winter Density’ in September/October, either in a greenhouse or in mild areas under cloches or in a coldframe

When sowing in summer, bear in mind that high temperatures can prevent some varieties from germinating Germination is the process by which a seed develops into a new plant. It starts with the seed coat absorbing water, expanding and splitting, which allows oxygen and water into the seed so its food reserves can be broken down and used by the embryo for growth. The first root (called the radicle) pushes into the soil to anchor the new plant in place and start absorbing water and nutrients. The first shoot (called the plumule) then grows upwards, out of the soil, towards the light. . So during hot spells, sow in the evening, water with cold water and provide some shade to keep temperatures down.

Sowing indoors

Sow lettuce seeds thinly in small pots, seedtrays or modular trays filled with moist, peat-free seed compost Seed compost is a free-draining compost formulated for germinating seed. It often contains a mix of fine materials including sterilised loam, coir, coarse sand or grit. It contains low levels of nutrients, as high levels could damage seedlings. , then keep in a warm, bright location such as on a windowsill or in a propagator A propagator is a portable, lightweight structure usually plastic, with a vented or unvented lid to provide a humid, slightly warmer atmosphere. It is useful to help seeds germinate and root cuttings. It may have adjustable, thermostatic temperature control. . Sowing indoors gives plants a head start when conditions outside are still too cold, and keeps the seedlings A seedling is a young plant grown from seed. safe from slugs and snails until they’re larger and more resilient. For more sowing tips, see our guides below.Carefully move seedlings into individual modules Small individual cells, usually in a tray, used for sowing seeds. The resulting seedlings can be transplanted with minimal root disturbance. /pots once they have a few leaves and are robust enough to handle – see our video guide to pricking out, below. Then plant them outside from spring onwards, once they’re growing strongly (see the Planting section below). During the colder months, they are best kept under cover, planted in a greenhouse border or large container.

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Sowing outdoors

Sow lettuce seeds thinly into prepared soil (see above), 1cm (½in) deep, in rows 30cm (1ft) apart. Sow a short row every fortnight to provide non-stop harvests and avoid gluts.Thin out lettuce seedlings A seedling is a young plant grown from seed. gradually to 15–30cm (6–12in) apart – check the seed packet for exact spacings. Thinning Pulling out some of the seedlings, usually along a row, so the remaining seedlings are spaced further apart. It reduces overcrowded, which can hinder their growth. is particularly important with hearting lettuces, as they may not form a firm head if overcrowded. The seedlings you remove can be added to salads.

Protect lettuce seedlings and young plants from slugs and snails. In early spring, you may also need to protect them from birds and cold temperatures by covering with cloches or plastic-free fleece.

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Sowing in containers

You can sow lettuces in large containers (at least 30cm/1ft wide) filled with moist, peat-free multi-purpose compost Can refer to either home-made garden compost or seed/potting compost: • Garden compost is a soil improver made from decomposed plant waste, usually in a compost bin or heap. It is added to soil to improve its fertility, structure and water-holding capacity. Seed or potting composts are used for growing seedlings or plants in containers - a wide range of commercially produced peat-free composts are available, made from a mix of various ingredients, such as loam, composted bark, coir and sand, although you can mix your own. . Growing bags are also suitable. They can then be kept outdoors or in a coldframe or greenhouse. Thin out the seedlings to the spacings given above. For more container-growing tips, see our easy sowing guides below.

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