Iceberg lettuce is the crisp, cool, crunchy lettuce of summer salads and burgers — a dense, pale-green head that stays crisp in the fridge longer than any other lettuce. It is also the most demanding lettuce to grow well: it needs cool, steady weather, even water and room to form its head, and it punishes heat and drought with bitter leaves and no head at all. Grown at the right time of year, though, it is deeply satisfying.
The secret of iceberg is timing. It takes 70–85 days to form a head, longer than romaine, and it wants that whole period cool — so in most zones it is a spring or autumn crop, not a midsummer one. This guide covers sowing, the wider spacing iceberg needs, watering for crisp heads, and the moment to cut, because an iceberg picked too early is a loose bunch of leaves and one picked too late is bitter and splitting.
Iceberg Lettuce at a glance
| Growing factor | What this crop needs |
|---|---|
| Sun | full sun |
| Soil pH | 6.0–7.0 |
| Days to germination | 7–10 |
| Days to maturity | 70–85 |
| Spacing | 12–18 inches |
| Water needs | moderate |
| Cold tolerance | hardy |
| Family | Asteraceae |
Starting seeds
Iceberg Lettuce can be started indoors or sown directly, and which you choose depends on your season. Indoor sowing gives you a head start in cold zones; direct sowing is simpler and avoids transplant shock. Either way, germination takes 7–10 days in warm, moist soil. Our seed-starting calculator can work out indoor sowing dates, and the seed-spacing calculator works out how many seeds you need for your bed.
This is a hardy crop, so it suits the cool parts of the year: in Zones 3–5 sow in early spring and again in late summer; in Zones 6–8 spring and autumn sowings do well, with summer sowings struggling in heat; in Zones 9–10 sow through autumn, winter and early spring; and in Zones 11–13, which are frost-free, grow it in the cooler months with afternoon shade. Check your dates with our frost-date calculator or the last-first frost lookup — and when in doubt, ask your local extension service.
Start iceberg indoors for the most reliable results: the seed germinates in 7–10 days, and indoor sowing lets you put out sturdy seedlings at exactly the right moment in spring. Sow thinly — iceberg seed is small and light helps it germinate — and do not let the seed tray get hot, or germination stalls.
Transplanting and planting out
Harden seedlings off for a week before planting out: put them outside for a few hours a day, increasing the time and exposure, and bring them back in at night. Plant out at the final spacing of 12–18 inches apart, in holes the same depth as the pot. Water each plant in well and mulch around (not against) the stems to hold moisture. Our plant-spacing calculator shows how many plants fit your bed at 12–18-inch spacing.
Soil and feeding
Iceberg Lettuce grows best in soil with a pH of 6.0–7.0, so test your soil before you plant — a cheap test kit tells you more than guessing ever will. Work in plenty of compost or well-rotted manure to improve structure and feed the soil life, and make sure the bed drains freely. Our soil-volume calculator and raised-bed soil calculator work out how much soil or compost your bed needs.
Feed generously through the season: work compost into the bed before planting and side-dress with a balanced fertiliser once plants are growing strongly. Hungry fruiting and leafy crops repay feeding with visibly bigger harvests, but too much nitrogen gives leaf at the expense of fruit, so follow the label. Our fertiliser calculator works out how much to apply.
Iceberg is a hungry crop for a lettuce: it needs rich, moisture-retentive soil to build a dense head. Dig in plenty of compost before planting, and feed lightly every couple of weeks while the heads are forming.
Watering
Water evenly and avoid letting the soil swing between soaked and bone dry. A deep soak once or twice a week beats a daily sprinkle, because it encourages roots to grow down where the soil stays cooler and moister. Mulch helps enormously here, holding moisture and keeping the soil temperature steady. Our watering calculator gives a starting point for your bed size and soil, and the watering schedule generator can build a routine around it.
Sunlight and temperature
Give Iceberg Lettuce full sun — at least six hours of direct sun a day, and more is better in most zones. Sun drives flavour and yield in this crop, and plants in shade stay leggy and unproductive. Our sunlight calculator can check whether your spot gets enough sun.
It is hardy and copes with cool weather and light frost, which makes it a spring and autumn crop in most zones. What it dislikes is heat: hot weather pushes it to bolt and turns leaves bitter, so in warm zones grow it in the cool season and give it afternoon shade.
Pests and diseases
The pests and diseases to watch for with Iceberg Lettuce are aphids, slugs and thrips.
Aphids cluster on tender new growth and under leaves, sucking sap and leaving sticky honeydew.
Slugs and snails chew ragged holes in leaves at night and love damp, mulched beds.
Thrips rasp leaf surfaces, leaving silvery speckled patches.
Prevention beats cure: rotate crops so the same family does not grow in the same bed year after year, clear debris at the end of the season, and inspect the undersides of leaves weekly. Our pest identifier helper can help you name a pest from its damage, and the plant-disease checker can narrow down a leaf problem.
Companion plants
Good companions for Iceberg Lettuce are marigolds, basil, onions and lettuce.
Marigolds are the classic companion: their roots and scent deter several soil pests, and their flowers bring in pollinators and beneficial insects.
Basil is said to improve the flavour of its neighbours and its scent confuses some pests; it also makes good use of the same sunny, well-watered bed.
Onions help mask the scent of their neighbours from pests, and their upright leaves take little light from the plants beside them.
Lettuce is a shallow-rooted, quick crop that fills the gaps between taller plants without competing hard for nutrients.
Plant companions in the same bed rather than in a separate corner — that is how they do their work. Our companion-planting finder can suggest more pairings for your bed.
Harvesting
Iceberg is ready about 70–85 days after sowing, when the head feels firm and solid when you squeeze it gently — a soft, loose head needs more time. Cut the whole head at the base with a sharp knife, leaving the roots in the ground. Harvest in the morning when the head is crisp, and do not wait once the head is firm: over-mature heads split, turn bitter and rot from the centre.
Rinse the head well, shake it dry and store it whole in the fridge, where it keeps far longer than any other lettuce — a week or more if it is dry. Do not cut it until you need it, and remove any damaged outer leaves first. If a head has started to bolt — the centre stretching up — harvest it at once and use the outer leaves, which are still edible even if the heart has gone bitter.
Common problems and fixes
| Problem | Likely cause | Fix |
|---|---|---|
| No head forms, just loose leaves | too hot, or plants too crowded | Give more space, grow in the cool season, and provide afternoon shade. |
| Brown edges inside the head | tip burn from uneven watering | Water evenly, avoid heavy feeding, and choose resistant types next time. |
| Head rots from the centre | water sitting in the head | Water at the base, not overhead, and improve airflow with wider spacing. |
No head forms, just loose leaves
Likely cause: too hot, or plants too crowded. Iceberg that stays loose and leafy has usually been too hot or too crowded. It needs cool weather and 12–18 inches of space to heart up, and in warm weather it may never form a head at all.
Brown edges inside the head
Likely cause: tip burn from uneven watering. Tip burn is brown, papery leaf edges inside the head, caused by calcium failing to reach fast-growing leaf tips when watering is uneven. Keep the soil consistently moist, do not overfeed, and accept that the outer leaves can be stripped away — the heart is often still usable.
Head rots from the centre
Likely cause: water sitting in the head. Rot starting in the centre of the head usually means water has sat in the heart, or the heads are packed so tightly that air cannot move. Always water at the base, space plants widely, and remove badly rotted heads so the problem does not spread to neighbours.
Frequently asked questions
How long does iceberg lettuce take to grow?
Iceberg lettuce takes 70–85 days from sowing to a firm head — longer than romaine. You cannot rush it: the head needs a long cool period to form properly.
Why won't my iceberg lettuce form a head?
The usual reasons are heat and crowding. Iceberg needs cool weather and 12–18 inches of space per plant to heart up.
When is iceberg lettuce ready to pick?
An iceberg is ready when the head feels firm and solid when squeezed gently. A soft, loose head needs more time; a very hard head that is starting to split is overdue.
Can you grow iceberg lettuce in summer?
Only in cool-summer zones. In most of the country, summer heat stops iceberg forming a head and pushes it to bolt.