PlantyBoxPot and soil
Troughs 15-20 cm (6-8 in) deep are enough. Fresh all-purpose mix. Space head lettuce 20-25 cm (8-10 in) apart; sow cut-and-come-again lettuce thickly in rows.
Light and position
Sun in spring and autumn, part shade in summer: heat and long days make it bolt (send up a flower stalk) and turn bitter.
Watering
Little and often: about every 2 days, keeping the soil cool and moist. The shallow roots dry out fast.
Feeding
A light nitrogen feed every 2 weeks. The cycle is short, so rich potting mix is often enough.
Harvest
Firm, full head (or 10-15 cm leaves for cut lettuce). Pick it before it bolts.
How to harvestCut-and-come-again: cut 3 cm above soil and it regrows. Heads: cut at the base; outer leaves can be picked earlier.
Common problems
It's bolting from heat or long days. Harvest right away; in summer choose bolt-resistant varieties and a shady spot.
Slugs and snails, especially after rain. Check in the evening and raise troughs off the ground.
Heat and thirst. Water more often and move the trough into part shade.
FAQ
When should I sow lettuce in pots?
From late winter to autumn depending on climate and variety. Sow a little every 2-3 weeks for a continuous harvest.
How do I harvest cut-and-come-again lettuce?
Cut the leaves 3 cm (1 in) above the soil: it regrows and can be cut 2-3 times.
Why does lettuce turn bitter?
In hot weather it sends up a flower stalk (bolts) and the leaves turn bitter. Pick it before, or grow it in spring and autumn.
