Lettuce is the crop everyone starts with and almost nobody grows really well. The packet promises sixty days; what you get is a flush of leaves in June, a spike of bitter, milky stems in July, and a gap for the rest of the year. None of that is bad luck. Lactuca sativa is a cool-season plant with two quirks that decide everything — its seed refuses to germinate in hot soil, and its leaves turn bitter the moment the plant decides to flower. Understand those two, and you can pick lettuce from April to Christmas. Here is the whole crop, from packet to plate.
- Botanical name Lactuca sativa (Asteraceae)
- Sow Mar–Sept outdoors · Feb indoors · Sept under cover
- Germination 3–10 days · needs light · stalls above 25 °C
- Harvest Baby leaf 25–30 days · full hearts 60–80 days
The two facts that change how you grow lettuce
First: lettuce seed has a heat switch. Above roughly 25 °C the embryo enters what botanists call thermo-dormancy — it does not fail, it deliberately refuses. This is a survival trait from a Mediterranean ancestor that had no interest in germinating into a July drought. It is also why the row you sowed in a heatwave never came up while the same packet sown in April was perfect. The fix is embarrassingly simple: sow in the evening, into a drill you have soaked with cold water, and shade the row with a plank or a board for four days. In a genuine heatwave, put the seed on damp kitchen paper in a sealed box in the fridge for 24–48 hours first; it will chit at 5 °C and can then be sown already sprouted.
Second: lettuce seed needs light. It is one of the classic positively photoblastic seeds. Bury it a centimetre deep in the way you would a bean and you have switched it off. Sow no more than 5 mm down — a scatter of fine soil or vermiculite you can still almost see through — and firm gently. Half the “my seeds never germinated” stories about lettuce are simply seed sown too deep, too warm, or both.
Choosing a type: four groups, four jobs
Every variety in our lettuce seed range belongs to one of four groups, and they are not interchangeable.
- Butterhead — soft, loose hearts. Fastest to a usable head, best flavour, shortest shelf life. Grosse Blonde Paresseuse, Appia, Hilde II, Rhénania.
- Cos / romaine — upright, crunchy midribs, the most cold-tolerant group. If you want lettuce in November, start here.
- Crisphead / iceberg — Great Lakes 118, Calmar, Ice Queen. The longest season and the fussiest about water, but the only group that keeps a week in the fridge.
- Loose-leaf & batavia — Salad Bowl, Lollo Rossa, Amerikaanse Roodrand, Australian Yellow. No heart at all, cut repeatedly, slowest to bolt. The most forgiving group for beginners.
Two specials are worth knowing about: Merveille des Quatre Saisons, a genuinely hardy red butterhead that earns its name, and celtuce, grown for its peeled stem rather than its leaves. Browse the whole species, including mixes and seed tape, under Lactuca sativa, and the organic range if you prefer untreated seed.
How to sow lettuce, step by step
- Pick your window Outdoors from March once soil hits 7 °C, right through to mid-September. February and October sowings need a windowsill or a cold frame.
- Prepare a fine, damp surface Lettuce roots are shallow and fibrous. A raked tilth over well-prepared soil beats deep digging every time.
- Sow thinly, 5 mm deep Water the drill first, sow into the wet, cover with dry soil. See direct sowing for the technique.
- Thin early and ruthlessly Thin at two true leaves: 10–15 cm for leaf types, 25–30 cm for hearting types. The thinnings are your first salad.
- Sow again in a fortnight A short row every two weeks — succession sowing — is the single biggest upgrade to a home lettuce supply.
Module-raising works well too, and dodges slugs: three seeds per cell, thin to one, plant out at four true leaves with the crown sitting proud of the soil, never buried. If your seedlings stretch on the windowsill, that is light, not warmth — see leggy seedlings, then harden them off before planting.
Growing on: water, bitterness and bolting
Lettuce is 95% water and roots in the top 15 cm of soil, which makes it the least drought-tolerant thing in the vegetable bed. Check the soil, not the leaves — a wilting lettuce at noon may be perfectly happy at six. Aim for one deep soak twice a week rather than a daily sprinkle; our watering guide explains why. Water in the morning so the foliage dries: wet leaves overnight invite downy mildew and grey mould.
The bitterness everyone complains about is real chemistry, not imagination. Lettuce carries a milky latex, lactucarium, in its stems and ribs, and the concentration climbs sharply as the plant prepares to flower. Bolting is triggered by long days plus heat — lettuce measures day length, which is why a June sowing bolts and an identical September sowing simply does not. So: pick in the cool of the morning, harvest before a heart splits or a central stem starts to elongate, and if a plant does bolt, pull it. It will not come back sweet.
Cut-and-come-again or full hearts?
Baby leaf, cut repeatedly
Sow thickly in a band, no thinning, cut with scissors 3 cm above the crown.
- First cut in 25–30 days
- Three to four cuts per sowing
- Loose-leaf, Lollo and mixes
Hearted lettuce, cut once
Thin to 25–30 cm and let each plant build a heart.
- Ready in 60–80 days
- One head per plant, then the space is free
- Butterhead, cos and iceberg
The same packet does both jobs — spacing is the only difference. For genuinely fast returns indoors, microgreens and sprouts from the sprouting range take days rather than weeks.
Common lettuce mistakes
- Sowing at midday in high summer — the drill is warmest exactly when you are most likely to be gardening. Sow in the evening from June to August.
- Covering the seed properly — a virtue everywhere else, a mistake here. Lettuce needs light on the seed. See how to germinate seeds.
- Sowing the whole packet in one go — thirty heads maturing in the same week is not a harvest, it is a compost problem.
- Planting seedlings too deep — a buried crown rots. The growing point must sit above the soil.
- Ignoring slugs for the first fortnight — nothing else eats a lettuce seedling so completely. Barriers, evening patrols and beer traps all work; see garden pests.
- Stopping in August — autumn is the easiest lettuce season of the year, and most gardeners simply never try it.
Frequently asked questions
Can you sow lettuce in September?
Yes, and it is one of the best sowings of the year. Soil is still warm, days are shortening so nothing bolts, and a September sowing under a cloche, cold frame or fleece gives you leaves through late autumn and again in early spring. Choose cos types or a hardy butterhead like Merveille des Quatre Saisons, and see what else to sow in September.
Why is my lettuce bitter?
Because it is bolting, or about to. Heat and long days push the plant into flowering, which raises the latex content of the ribs. Harvest earlier, pick in the morning, keep the plants evenly watered, and switch to bolt-resistant loose-leaf types for midsummer.
How long does lettuce take to grow from seed?
Baby leaf is cuttable in 25–30 days. A full heart takes 60–80 days depending on the type: butterhead is fastest, iceberg slowest. Autumn and winter crops take considerably longer because growth all but stops below about 6 °C.
Can I grow lettuce in pots?
Very well — it is arguably the ideal container crop, since shallow roots suit a 15–20 cm deep pot and you can move it into shade in July. Use a wide, shallow container, never let it dry out, and read our container growing guide.
Lettuce rewards small, frequent effort far more than it rewards a big spring push. Sow a short row now, another in a fortnight, and keep going until the light runs out. Round the salad bowl out with rocket, corn salad, endive and chicory, or browse all our vegetable seeds and the rest of our growing guides. If you plant one thing this week, make it a band of loose-leaf lettuce and a row of cos: one feeds you in three weeks, the other still will in November.
