How to Grow Lettuce All Season – Sowing, Bolting and Harvest

Lettuce at a glance

Contents

• Lettuce at a glance
• Which type of lettuce should you grow?
• Succession sowing – the key to lettuce all season
• How to sow lettuce step by step
• Spring sowing: the first lettuce of the year
• Why won't lettuce seed germinate in summer heat?
• What is bolting and how do you prevent it?
• Late summer sowing and lettuce under row cover
• Can you grow lettuce in winter?
• Zone table: sowing and harvest in USDA zones 3–6
• Leaf by leaf or whole heads – how should you harvest?
• Water, feeding and weeds
• Slugs, aphids and downy mildew
• Growing lettuce in containers and raised beds
• Common mistakes
• Frequently asked questions

Which type of lettuce should you grow?

"Lettuce" is not one plant but several growing forms of the same species, sown the same way but behaving completely differently in heat, in harvest and in how long they stand. Match the type to the season and half the work is done.

Loose-leaf lettuce

Loose-leaf types never form a head. The leaves sit in an open rosette you pick from the outside in, or cut 2–3 cm (1 in) above the soil and let regrow. It is the fastest type – baby leaves in about five weeks – and the most forgiving. 'Black Seeded Simpson' and the frilly 'Lollo' types are the standards.

Oakleaf

Oakleaf is a loose-leaf lettuce with deeply lobed leaves. It bolts noticeably later than other leaf types and is one of the few forms that reliably overwinters in a cold climate: 'Salad Bowl' and 'Red Salad Bowl' both stand under a cloche through winter in zones 5–6.

Butterhead

Butterhead forms a soft, loosely folded head of buttery leaves. It tastes most like lettuce, but wants space, time and even moisture and bolts sooner in heat. 'Buttercrunch' is the spring workhorse, 'Tom Thumb' a tennis-ball-sized cultivar for short seasons.

Romaine and cos

Romaine – cos – forms an upright, elongated head with stiff midribs and crisp leaves. It is the most heat-tolerant heading type and stays usable in July far longer than butterhead. 'Parris Island Cos' is the full-size standard; 'Little Gem' is a mini cos, a dense 12–15 cm (5–6 in) head that finishes faster and fits raised beds well.

Crisphead and batavia

Crisphead – iceberg – forms a hard, round, brittle head, takes the longest at 75–85 days, needs the most space and will not head up if it dries out at the wrong moment. Batavia sits in between – crisp leaves like iceberg, a loose head like leaf lettuce – and is one of the best types for summer. 'Nevada' and 'Muir' are sold for heat tolerance.

Succession sowing – the key to lettuce all season

This is what separates a three-week lettuce season from a seven-month one. Succession sowing means putting in a small amount at regular intervals so three generations always run: one being picked, one half grown and one just sown.

How often should you sow?

Every three weeks is enough in spring and autumn, when plants grow slowly and stand a long time. In midsummer drop to every two weeks: everything grows twice as fast, and a finished lettuce has only days before it turns bitter. A rule easier to remember than a date: sow the next batch the day you see the first true leaves on the last one.

How much should you sow each time?

Work backwards from what you eat. A household having a bowl of salad a day gets through four to six loose-leaf plants a week. At a three-week interval that is twelve to eighteen plants per sowing – barely two metres (6 ft) of row. One packet covers a season.

A sowing schedule that works

Set a reminder on your phone. Succession sowing almost never fails on knowledge – it fails because midsummer is a busy week and ten minutes with a seed packet never feels urgent. One trick makes the schedule run itself: divide the bed into four squares and sow one square at a time in rotation. By the time you come back to square one it is picked and empty – proper crop rotation in miniature, inside a single season.

How to sow lettuce step by step

1. Decide between direct sowing and modules. Loose-leaf is easiest direct sown, and it is the only sensible method when you sow a metre of row every fortnight. Butterhead, romaine and crisphead come out more even started in modules: you skip thinning, and a 5 cm (2 in) transplant survives a slug attack that kills a seedling. Plant modules out by the fourth true leaf, or the roots suffer.
2. Rake a fine seedbed. Lettuce seed is small and cannot push through clods. Clear stones and debris from the top 5 cm (2 in).
3. Sow shallow. 0.5–1 cm (1/4–1/2 in), never deeper – lettuce seed needs light. Scatter thinly along a shallow drill and cover with just enough fine soil to hide it.
4. Water with a fine rose. Water the drill before sowing so moisture comes from below. A coarse jet floats the seed into a clump.
5. Keep the surface damp for a week. This decides whether the sowing works. Fleece or a plank over the drill holds moisture in – lift the plank the moment shoots appear.
6. Thin in two stages. To 5 cm (2 in) at the seed-leaf stage, then to final spacing at three or four true leaves. The second thinning is your first harvest: ready-made baby leaf.
7. Plant out modules in the evening. Crown exactly at soil level – plants buried too deep collect soil in the crown and rot. Water in straight away.
8. Label the row with cultivar and date. In July, with four sowings in one bed, it is the only way to know what is ready when.

Spring sowing: the first lettuce of the year

Lettuce is one of very few vegetables that genuinely prefers it cool. Germination from 4–5 °C (39–41 °F) and best growth at 15–18 °C (59–64 °F) make it a spring and autumn crop in any cold climate – and the spring window is the best part of the season, not just the earliest.

Starting indoors

Sow in modules four to six weeks before planting out. Keep them cool and very bright; 15–18 °C (59–64 °F) is plenty, and warmer only produces long, floppy seedlings. An unheated greenhouse or a cold porch beats a warm kitchen windowsill.

The first outdoor sowing

Sow as soon as the soil can be raked and holds about 5 °C (41 °F), and lay fleece over the row. It lifts soil temperature a few degrees, protects against night frost and keeps birds and cutworms off – under cover you can sow two to three weeks earlier. Hardened-off plants take −4 °C (25 °F), while soft plants from a warm window are damaged by light frost, so harden them off for a week first.

What to sow alongside lettuce

Lettuce is a useful catch crop – it finishes before slower neighbours need the room. Sow it as a marker crop in a carrot row: lettuce is up in five days and shows where the row runs while the carrot seed is still thinking about it. More in the guide to growing carrots and the rundown of companion planting.

Why won't lettuce seed germinate in summer heat?

Lettuce seed has a built-in switch called thermodormancy. In soil warmer than roughly 25 °C (77 °F) germination shuts down – not because the seed is dead, but because it is programmed to wait out the heat. That is why seed which sat still for three weeks comes up all at once after one cool rain in late summer.

The soil surface also runs far hotter than the air. Bare dark soil in sunshine can sit 15 °C (27 °F) above air temperature: 22 °C (72 °F) in the shade may be 35 °C (95 °F) in the drill – and the seed lies in the top centimetre where it is hottest.

Five ways to get summer sowings up

• Sow in the evening. The seed takes up water in the first few hours, and that step is decisive. If it happens overnight, dormancy never sets in.
• Water the drill with cold water. It drops soil temperature several degrees for a few hours – exactly the window needed.
• Shade the sowing. A plank, shade cloth or doubled fleece over the row until shoots appear.
• Pre-chill the seed. Leave it on damp kitchen paper in the fridge for three to five days, then sow as it starts to split. This is the standard trick for midsummer sowings.
• Start modules in the shade. A tray on the north side of the house is easy to keep cool and damp. Plant out at four leaves.

Old seed is extra sensitive. Lettuce seed germinates well for three to four years stored cool and dry, but the ability to germinate warm goes first – use the freshest seed for summer sowings.

What is bolting and how do you prevent it?

Bolting is when lettuce stops making leaves and sends a flower stalk straight up out of the centre. The plant goes tall, the leaves narrow and stiff, and the flavour turns from mild to distinctly bitter.

The bitterness is chemistry, not imagination. Lettuce contains a white latex carrying sesquiterpene lactones – mainly lactucin and lactucopicrin. Levels are low in a young plant and rise sharply once flowering starts, which is why a bolted lettuce cannot be rescued: the bitterness is in the leaves, and no cooking removes it.

What triggers it?

Two signals combine. The first is day length – lettuce is a long-day plant and gets its flowering cue when days get genuinely long, in the north the weeks around the solstice. The second is heat, especially warm nights above 20 °C (68 °F). On top of that comes stress, and drought is the most common trigger in a home garden: a plant that dries out for a day reads it as the end of the season and switches to reproduction. Root disturbance from planting out too late and overcrowding do the same.

Keeping lettuce standing

• Water evenly. The single most effective measure. Better a good soak twice a week than a splash every day.
• Give part shade in midsummer. Four to six hours of sun is plenty. Shade from a row of beans or a cucumber trellis lowers both air and soil temperature.
• Mulch. Five centimetres (2 in) of grass clippings or straw between plants keeps the soil cooler and damper.
• Pick the right type. Batavia, oakleaf and romaine stand far longer than butterhead and crisphead.
• Harvest earlier. A few days early always beats one day late.
• Skip the worst weeks. Many growers sow no heading lettuce at all from mid-June to mid-July and let loose-leaf and batavia cover that gap.

Is a bolted lettuce any use?

Not the leaves. But let one plant run up and flower. The flowers are small and yellow like a dandelion, bumblebees work them, and you collect seed a few weeks later – lettuce is self-pollinating, so the offspring come true as long as one cultivar flowers at a time. A bolted plant is free seed for next year.

Late summer sowing and lettuce under row cover

Late summer is lettuce's second-best window, and the one most people skip. From early August nights cool off, day length shortens and the flowering signal fades – cultivars that bolted in ten days in July now stand for weeks.

Make the last outdoor sowings in early to mid August in zones 5–6, one to two weeks earlier in zones 3–4. Count backwards from your average first autumn frost: loose-leaf needs six to eight weeks, heading types ten to twelve.

Fleece adds a month

Lay fleece over the rows when nights start creeping toward freezing. It gives two to four degrees of protection, moving the last picking from mid-October to mid-November. Peg the edges down properly – autumn is windy.

Lettuce takes more cold than most people expect. Plants that grew slowly in cool weather harden themselves and survive repeated nights down to −5 °C (23 °F), often glassy in the morning and fully recovered by afternoon. Never pick a frozen plant – the leaves go to mush as they thaw.

Lettuce in the greenhouse after the summer crops

A greenhouse usually stands empty from October, exactly when it is most useful for lettuce. Plant lettuce in as soon as the tomatoes and the plants from the guide to growing cucumbers are cleared. An unheated greenhouse adds four to six weeks over open ground, more with fleece inside it.

Can you grow lettuce in winter?

Yes, with the right expectations. Below roughly ten hours of daylight plants effectively stop, so winter lettuce is not about growing in winter – it is about having full-grown plants in place before the light runs out, then picking off them.

Overwintering for an early spring crop

Sow hardy cultivars in early autumn. Plants should reach hand size but no more before growth stalls – bigger plants take more cold damage and often bolt in spring. Cover with fleece or grow in a tunnel, and water sparingly so grey mould does not take hold.

When days pass ten hours in late winter the plants restart, and you have pickable lettuce weeks before the first spring sowing is up. Cultivars used for this are 'Winter Density', 'Arctic King', 'Valdor', 'Rouge d'Hiver' and the oakleaf 'Red Salad Bowl'.

Corn salad is not lettuce

A confusion worth clearing up: corn salad, also called lamb's lettuce or mâche (Valerianella locusta), is not the same species at all. It is far hardier, sown in late summer, survives several degrees of frost uncovered and is picked all winter wherever the ground is not frozen. For green leaves in December it is the safer bet – as are overwintering spinach and Asian greens such as mizuna.

Zone table: sowing and harvest in USDA zones 3–6

Lettuce grows in all of these zones, so the zone says nothing about hardiness – it sets how long the window is at each end. The figures are guides; a warm south-facing bed against a wall behaves like half a zone milder.

Two things are worth noticing. The gap between zone 3a and 6b is about ten weeks at sowing but only six at harvest – lettuce makes up time where summer days are long. And bolting risk does not shift with the dates: the solstice weeks are critical in every zone, because the day-length signal is the same everywhere.

Leaf by leaf or whole heads – how should you harvest?

Harvest method decides how much a bed yields, and the difference is bigger than most expect: the same row can give one picking or four.

Leaf by leaf

Pick the outermost, largest leaves and leave the heart untouched, never more than a third at a time. This works on loose-leaf, oakleaf and most romaine, and gives the longest picking period per plant – six to eight weeks is normal.

Cut and come again

Cut the whole rosette with scissors 2–3 cm (1 in) above the soil, above the growing point. The plant pushes new leaves from the stub and is ready again in two to three weeks – expect two to four rounds. This is the method for baby leaf and thickly sown salad mixes, and the one that yields most per square metre. Cut in the morning while the leaves are full of overnight water. Keep them in a bag with a sheet of kitchen paper in the fridge crisper, where loose-leaf holds four to six days and a whole head up to two weeks.

Whole heads

Butterhead, crisphead and full-size romaine are cut as whole heads, at the stem just below the lowest leaves, when the head feels firm under light pressure – hard as a ball means you are a few days late. Leave 5 cm (2 in) of stem in the ground and many cultivars push a second, smaller flush.

Water, feeding and weeds

Water

Lettuce roots shallowly, mostly in the top 15 cm (6 in), and cannot reach deeper moisture. Allow 15–25 mm (0.6–1 in) a week when it is not raining, in a couple of proper soakings rather than daily splashes. Water at the base in the morning – wet leaves overnight are exactly what downy mildew wants. If lettuce turns bitter without bolting, drought stress is almost always the cause.

Feeding

Lettuce wants readily available nitrogen, but not much of it. A bed given two to three litres of compost per square metre in spring carries the whole season. If growth stalls and leaves are pale, give a weak liquid feed. Do not overdo it: excess nitrogen gives large, soft leaves with thin cell walls – a magnet for aphids and slugs.

Weeds and rotation

Lettuce plants are short and compete badly. Keep the bed clean for the first four weeks; after that the leaves shade out most of it. Hoe shallowly – deep hoeing damages the surface roots.

Lettuce belongs to the daisy family with endive, chicory and Jerusalem artichoke, and should not sit in the same ground year after year. Two to three years is enough, shorter than for alliums and brassicas. Because it finishes in one to two months it slots in as a catch crop almost anywhere.

Slugs, aphids and downy mildew

Slugs

Slugs are lettuce's biggest enemy by a wide margin. Seedlings vanish overnight, and in a wet year no single measure is enough. Combine several: plant out modules too big to be eaten in one night; clear hiding places such as planks and long grass at the bed edge; water in the morning so the surface is dry by evening; hand-pick at dusk after rain; and use ferric phosphate pellets, approved for organic growing, around new transplants. Lettuce in a raised bed suffers noticeably less – one of the stronger arguments for growing salad crops in raised beds.

Aphids

Both green aphids on the leaves and lettuce root aphid (Pemphigus bursarius) occur. The root aphid is worse: the plant wilts at midday although the soil is moist, and pulling it up reveals roots coated in a white, waxy powder. There is no treatment – rotate, and choose cultivars listed as root-aphid resistant. Leaf aphids wash off with water, or look after themselves if ladybirds and hoverfly larvae are working. Insect mesh over the row is the simplest protection in a small garden.

Downy mildew and rots

Lettuce downy mildew (Bremia lactucae) shows as pale yellow, angular patches on the upper leaf surface and a greyish white fuzz underneath, favoured by damp weather, dense sowing and overhead watering. The fixes are airy spacing, watering at the base, removing affected leaves and resistant cultivars. It spreads fast in thickly sown baby leaf, so in wet weather cut a batch early. Grey mould and lettuce drop (Sclerotinia) attack plants standing close and damp, especially under cover in autumn, and respond to the same things: air, longer rotation, and binning affected plants rather than composting them.

Growing lettuce in containers and raised beds

Few vegetables suit a limited volume as well. Lettuce is shallow-rooted, fast and needs no support – one window box produces leaves every week for months. Requirements are modest: at least 15 cm (6 in) of soil depth for loose-leaf, 20–25 cm (8–10 in) for heading types, drainage holes and a compost that holds moisture. A 60 × 20 cm (24 × 8 in) box holds six to eight loose-leaf plants or three butterheads.

What kills container lettuce is always water. A pot in full sun dries out in half a day in July, and one drying-out triggers bolting. Give pots morning sun and afternoon shade, use one large container rather than two small, and mulch with a thin layer of grass clippings.

In a raised bed, grow lettuce in a grid rather than rows – 15 × 15 cm (6 × 6 in) for loose-leaf, 25 × 25 cm (10 × 10 in) for heading types. The space is used better and the leaves shade the soil sooner, keeping it damp. More on construction and soil mix in the guide to raised bed gardening.

Common mistakes

• Sowing the whole packet at once. Thirty heads in one week and nothing in late summer. Sow a metre of row every 2–3 weeks instead.
• Sowing too deep. Lettuce seed needs light. Buried under 2 cm (3/4 in) only a fraction comes up. One centimetre at most.
• Letting the surface dry during germination. The first five to eight days decide everything. One drying-out kills the sowing.
• Sowing midday in summer heat. Above 25 °C (77 °F) the seed goes dormant. Sow in the evening, water cold and shade the row.
• Skipping the thinning. Crowded lettuce never heads up, dries out faster and invites downy mildew. Thin in two stages and eat what you pull.
• Harvesting too late. A few days late in July is all it takes for bitter leaves.
• Taking the whole plant when picking leaves would do. Leaf by leaf or cut and come again yields three to four times more.
• Forgetting the late summer sowing. August and September are lettuce's second-best window: cool nights, no flowering signal and picking into November under cover.

Frequently asked questions

When should I plant lettuce?
Sow the first batch under fleece as soon as the soil can be raked – mid March in zone 6, early May in zone 4 – and uncovered two to three weeks later. Then sow a short row every 2–3 weeks until mid to late August. A final sowing in early autumn can be overwintered under cover for picking in late winter.

How often should I plant lettuce for a continuous harvest?
Every three weeks in spring and autumn, every two weeks in midsummer when growth doubles in speed. An easy rule is to sow the next batch the day the previous one shows its first true leaves – that adjusts the interval to the temperature by itself. Sow one metre of row often rather than ten metres once.

Why is my lettuce bitter and going to seed?
That is bolting, triggered by long days around the solstice combined with heat – and almost always by drought stress. The plant switches from leaves to flowering and the bitter compounds in its latex rise sharply. The leaves cannot be saved. Water evenly, give part shade in midsummer, choose batavia or oakleaf, and harvest earlier.

How deep do you plant lettuce seeds?
0.5–1 cm (1/4–1/2 in), never deeper. Lettuce seed needs light to germinate, so a thin layer of fine soil that barely hides it is exactly right. Sown deeper, only a small fraction comes up. Keep the surface evenly damp for the first five to eight days – the single biggest factor in whether the sowing works.

Why won't my lettuce seeds germinate in summer?
Lettuce seed goes dormant when soil is warmer than about 25 °C (77 °F), and bare soil in sun runs far hotter than the air. Sow in the evening, water the drill with cold water and shade the row until shoots appear. Most reliable of all is to pre-chill the seed on damp paper in the fridge for three to five days and sow as it starts to split.

Can you harvest lettuce more than once?
Yes, on loose-leaf, oakleaf and most romaine. Pick the outer leaves and leave the heart, or cut the whole rosette 2–3 cm (1 in) above the soil, above the growing point. The plant pushes new leaves within two to three weeks and gives two to four rounds. Butterhead and crisphead are cut once, as whole heads.

How much frost can lettuce take?
Plants that grew slowly in cool weather harden themselves and survive repeated nights down to −5 °C (23 °F), often glassy in the morning and fully recovered by afternoon. Plants moved straight from a warm windowsill are damaged by light frost, so harden them off first. Never pick a frozen plant – wait until the leaves thaw.

What is the best lettuce to grow in hot weather?
Batavia types such as 'Nevada' and 'Muir', oakleaf and romaine stand far longer in heat than butterhead and crisphead. Loose-leaf also works well, since you pick the leaves before the plant has time to bolt. Combine with part shade, mulch and even watering and you can run through the hottest weeks without a gap.

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