Romaine lettuce is the upright, crisp-hearted lettuce behind every good Caesar salad, and it is one of the most reliable leafy crops a gardener can grow. Its tall, sturdy leaves form a loose upright head, and unlike iceberg it is forgiving to harvest: you can pick outer leaves for weeks, or cut the whole head when it is full. It is fast, too — ready in 60–70 days — and it fits neatly between slower crops in a busy bed.
Romaine is a cool-season crop, and that is the one thing to get right: sow it in spring and again in late summer, and it will give you crisp leaves for months. Sow it in the heat of midsummer and it bolts, turns bitter and goes to seed before you have eaten a leaf. This guide covers sowing, spacing, watering for crisp leaves, and how to harvest so one planting feeds you for weeks.
Romaine 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 | 60–70 |
| Spacing | 8–12 inches |
| Water needs | moderate |
| Cold tolerance | hardy |
| Family | Asteraceae |
Starting seeds
Romaine 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.
Romaine seed is small, so sow thinly and barely cover it — light helps it germinate. Sow in modules for the earliest crop, or direct in rows where the plants will grow.
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 8–12 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 8–12-inch spacing.
Soil and feeding
Romaine 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.
Romaine wants rich, moisture-holding soil: hungry, fast-growing leaves need nitrogen and steady water. Dig in plenty of compost before sowing, and a light liquid feed every couple of weeks keeps leaves growing fast and tender.
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 Romaine 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 Romaine 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 Romaine 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
Romaine is ready to harvest about 60–70 days after sowing, but you do not need to wait for a full head. Start picking the outer leaves once they are big enough to eat, working from the outside in — the plant keeps growing from the centre, and one planting can feed you for weeks. For a full head, wait until the leaves stand tall and the heart feels firm when you squeeze it gently, then cut the whole plant at the base with a sharp knife.
Harvest in the morning, when leaves are crisp and full of water, and rinse and dry them well before storing — wet leaves rot fast in the fridge. In cool weather a cut romaine stump will often regrow a small second head if you leave the roots in place. Once the plant starts to stretch upwards and the centre opens, it is bolting: harvest what is left quickly, because the leaves turn bitter fast.
Common problems and fixes
| Problem | Likely cause | Fix |
|---|---|---|
| Leaves taste bitter | heat stress or bolting | Grow romaine in the cool season, give afternoon shade, and harvest before plants bolt. |
| Brown edges on inner leaves | tip burn from uneven watering | Water evenly and avoid heavy fertiliser late in growth; choose resistant types next season. |
| Plants bolt and run to seed | long hot days | Sow in spring and late summer, not midsummer, and harvest early in warm weather. |
Leaves taste bitter
Likely cause: heat stress or bolting. Bitter romaine is almost always a heat problem. Lettuce produces bitter compounds when it is stressed by heat or drought, and once a plant starts bolting the bitterness increases fast.
Brown edges on inner leaves
Likely cause: tip burn from uneven watering. Tip burn shows as brown, papery edges on the inner leaves of the heart, and it is caused by calcium not reaching the fast-growing leaf tips — usually because watering has been uneven or the plant grew too fast on heavy fertiliser. Keep watering steady, avoid overfeeding, and pick the damaged outer leaves off; the heart is often still fine underneath.
Plants bolt and run to seed
Likely cause: long hot days. Bolting is romaine's response to long days and heat: the stem stretches, the leaves open out, and a flower stalk shoots up. Once it starts there is no reversing it, so the answer is prevention — sow at the right time of year, give shade in hot weather, and harvest promptly.
Frequently asked questions
How long does romaine lettuce take to grow?
Romaine lettuce takes 60–70 days from sowing to a full head, but you can start picking outer leaves much sooner — usually within five or six weeks. Picking outer leaves extends the harvest for weeks, while cutting the whole head gives you one big harvest.
Can you cut romaine and will it regrow?
Yes — romaine is one of the best cut-and-come-again lettuces. Pick the outer leaves and leave the centre growing, and the plant will keep producing for weeks.
Why is my romaine lettuce bitter?
Bitterness is caused by heat, drought or bolting. Grow romaine in the cool season, water evenly so the soil never dries out, give afternoon shade in warm weather, and harvest young leaves.
How far apart should romaine lettuce be planted?
Space romaine plants 8–12 inches apart. Closer spacing suits baby-leaf picking, where you harvest young; wider spacing gives the plants room to form full, firm heads.