Growing loose-leaf lettuce in a pot or trough
Head lettuce wants space and patience: you wait ten weeks and harvest once. Loose-leaf lettuce inverts that. You cut the outer leaves and the heart keeps growing, week after week. For a windowsill trough or a balcony rail, that is the difference between one salad and six weeks of harvests.
At a glance
- Light
- 4 to 6 hours, partial shade is fine
- Pot depth
- Trough 15 to 20 cm deep
- Sowing
- March to September, every three weeks
- Harvest
- From 5 to 7 weeks, then continuously
- Water
- Regularly — the leaves wilt fast
- Level
- Easy
Sowing
Sow half a centimetre deep in rows fifteen centimetres apart. Lettuce seed germinates on light, so cover it only thinly — sown too deep it simply never comes up.
Above 25°C lettuce seed goes dormant. In midsummer, sow in the evening and keep the trough shaded for the first few days.
Care
Thin to ten centimetres apart once the seedlings have four leaves. Do not bin the thinnings — that is your first mini harvest.
Lettuce is almost entirely water and shows it: in dry compost the leaves flop within half a day and the flavour turns bitter. A trough in full afternoon sun dries out faster than you expect.
Harvesting
Cut the outer leaves two centimetres above the compost and leave the heart standing. New leaves appear within a week, giving five or six harvests from the same plant.
Harvest in the morning if you can. Leaves that have sat in afternoon sun are limper and keep less well in the fridge.
Common mistakes
Cutting the whole plant at once — then it is finished. The entire point is that the heart stays put.
Bolting shows as a stem suddenly shooting upwards, caused by heat or drought, and from then on the leaves taste bitter. Just sow again.
Frequently asked questions
How long does loose-leaf lettuce keep producing?
Five or six harvests from the same plant is normal, roughly six to eight weeks. After that the leaves toughen and it is better to resow.
Can lettuce grow in shade?
Better than most vegetables. Four hours of light is enough, and in summer partial shade is actually preferable: less heat means later bolting.
Why does my lettuce taste bitter?
Bitterness comes from heat or drought, often just before the plant bolts. Water evenly and keep the trough out of full afternoon sun in summer.
Updated on 2026-08-25
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