Lettuce from March to November, and why summer sowings fail

You can sow lettuce for most of the year in the UK. Outdoors, sow from late March to early September. Indoors, start from late February for the earliest heads, and again from mid-September to mid-October for lettuce under cover into the autumn.

Each sowing only gives about a month of picking, so the secret is a short row every two to three weeks. The other thing to know is that lettuce seed can refuse to germinate in hot soil, which catches out a lot of summer sowings.

Through the year

When	What to do
Late February to early April	Sow indoors in modules, plant out from late March
Late March to May	Sow outdoors, any type
June to August	Sow outdoors in a cool spot, or in modules somewhere shaded
Early September	Last outdoor sowings, for autumn picking
Mid-September to mid-October	Sow hardy types indoors or under cover for autumn and early winter

The dates assume a typical lowland garden in England or Wales, with a last frost around 20 April and a first frost around the end of October. In Scotland and the north, start a couple of weeks later in spring and finish earlier in autumn. In the south-west and in cities, both ends of the season stretch further.

Why summer sowings fail

Lettuce seed goes dormant in warm soil. Above about 25 °C, much of it simply won’t come up, and a sunny bed in July can easily be warmer than that at the surface.

A few things get round it:

1. Sow in the evening, so the seed spends its first hours in cooler soil.
2. Water the drill before sowing, and again lightly afterwards.
3. Sow in a spot that’s shaded in the afternoon, or shade the row with a board until the seedlings show.
4. Or sow in modules and keep them somewhere cool, like a shady corner or a north-facing windowsill, then plant out.

Summer lettuce also bolts quickly in heat and dry soil. Varieties sold as slow to bolt, and loose-leaf types you pick a few leaves from at a time, cope best.

How to sow

1. Make a shallow drill, about 0.5 cm deep. Lettuce seed is small and needs light covering.
2. Sow thinly along the row, with rows 30 cm apart.
3. Thin seedlings to about 25 cm apart for hearting lettuce. Loose-leaf types can stay closer.
4. In modules, sow two or three seeds per cell and thin to one.

Lettuce grows well near carrots, radishes, beetroot, strawberries and onions, and it’s handy for filling gaps between slower crops.

Picking

Lettuce is ready 40 to 85 days after sowing, depending on the type and the time of year. Loose-leaf types can be picked a few leaves at a time from about a month. Hearting lettuces are ready when the heart feels firm when you press it gently.

Pick in the morning, when the leaves are crisp, and cut hearting types at the base.

Late sowings are hardy to about -4 °C, but leaves damaged by frost go limp. A cloche or a cold frame keeps autumn lettuce going into November.

Common problems

Slugs. The main pest. Check rows after rain and at night, and keep young plants clear of long grass and debris.

Bolting. A tall flower stalk in hot, dry weather. Sow little and often, keep the soil moist and pick promptly.

Aphids. Clusters under the leaves or around the roots. Wash them off, and grow a few calendula or other flowers nearby to bring in hoverflies.

Set your own frost dates on the lettuce page, or see how lettuce fits between other crops in our companion planting guide.