Zone 13 is the hottest USDA zone and the only one that is frost-free year-round, with average winter lows above 60°F. There is no last spring frost and no first autumn frost to plan around, so in Zone 13 you plant by heat and by the wet and dry seasons, not by frost. The limits on what grows are heat, humidity, rain and pests rather than cold. All numbers below are published ranges, not promises for your garden: check your local extension service before you plant.
Romaine lettuce is the most reliable lettuce for Zone 13: upright, crisp and heat-tolerant compared with other lettuces, and ready in about two months. It is still a cool-season crop — heat makes it bolt and turn bitter — but among lettuces it gives you the best chance in the tropics. Sow it in the coolest months, give it afternoon shade and steady water, and pick it young for the sweetest leaves.
Zone 13 timing for romaine lettuce
The table below is the whole plan in one place.
| Step | Zone 13 timing |
|---|---|
| Average winter low | Above 60°F |
| Last spring frost | None — frost-free year-round |
| First autumn frost | None — frost-free year-round |
| Best planting window | Coolest months only, roughly November to February |
| Start indoors | Optional head start indoors a few weeks before transplanting |
| Direct sow outdoors | Sow direct the coolest months, roughly November to February, or transplant seedlings |
| Days to germination | 7–10 days |
| Days to maturity | 60–70 days |
| Cold tolerance | hardy |
When to sow romaine lettuce in Zone 13
Sow romaine in the coolest months, roughly November to February, in small batches every two weeks. It matures in about two months, so a sowing made at the start of the cool season has time to form full heads, while a late sowing can be picked young as loose leaves. Stop sowing once heat builds, and resume when the cool months return. Use the seed-starting calculator to work backwards from your transplant date.
Starting romaine lettuce: indoors or direct sowing
Romaine can be started indoors or direct-sown. Starting indoors protects seed from heavy rain and gives you sturdy transplants; direct sowing is simpler and works well if the seed bed stays damp. Sow seed shallowly, keep it moist until germination in about a week, and thin or transplant to the spacing in the table.
Soil, spacing and sun
Romaine Lettuce needs full sun. Space plants 8–12 inches apart — crowded plants compete for light, water and air, and disease spreads faster between touching leaves in humid tropical air. Romaine wants rich, moisture-holding soil with plenty of compost and full sun in the cool season — though afternoon shade is a real help in Zone 13. Work compost into the bed before sowing, keep the soil evenly moist, and mulch lightly to keep roots cool.
Watering romaine lettuce in Zone 13
Water needs are moderate, but lettuce is shallow-rooted and wilts fast. Water little and often, preferably in the morning, and never let the bed dry out completely — drought makes romaine bitter and triggers bolting. A light mulch and a little afternoon shade reduce watering needs noticeably. Use the watering calculator to work out how much water your bed needs.
Companion plants
Good companions for romaine lettuce include marigolds, basil, onions, lettuce. These are the companions listed for this crop in standard horticultural references: they share similar needs, and some, like marigolds, are traditionally planted to help confuse or deter pests. Plant companions in the same bed or nearby, not in a separate corner of the garden, so they actually share the space. Avoid planting heavy feeders that will compete for the same nutrients in the same spot.
Common pests and problems
The pests to watch for are aphids, slugs and thrips. Slugs are the main problem on damp nights, so keep mulch back from stems and check after rain. Aphids hide in the folds of the head and can be washed off. Thrips cause silvery patches on leaves — row cover over young plants is the best prevention.
Harvest and storage
Harvest romaine when heads are firm and full, about two months after sowing, by cutting at the base — or pick outer leaves over several weeks and let the centre keep growing. Pick in the morning when leaves are crisp, wash well, and use the same day. Once the centre starts to stretch upwards, the plant is bolting: harvest what is usable and move on.
Succession and rotation in Zone 13
Succession sowing works in Zone 13, but only inside the cool season: sow a small batch every two to three weeks while the weather stays mild, so the harvest stretches out instead of arriving all at once. Once heat builds, stop sowing — a late batch will bolt before it is worth picking. Rotate crops so romaine lettuce does not follow another Asteraceae family crop in the same bed next season. Keep notes on what you sowed and when: in a climate with no frost dates, your own records are the most useful planting guide you will have for the next cool season.
Related Zone 13 guides
More Zone 13 guides: Iceberg Lettuce in Zone 13 and the same crop in a cooler zone, Romaine Lettuce in Zone 11. The December in Zone 13 guide shows what else to plant in that month, and the planting calendar hub brings all the Zone 13 guides together.
Frequently asked questions
When should I plant romaine lettuce in Zone 13?
Sow romaine lettuce in the coolest months, roughly November to February. Zone 13 is frost-free with winter lows above 60°F, so there is no last or first frost date to work from — plant by the cool season, not by frost. Check your local extension service for the best sowing weeks in your area.
Is romaine really better than other lettuces in Zone 13?
Yes — it tolerates heat better than iceberg or butterhead and forms a usable head in conditions where other lettuces fail. It is still a cool-season crop, but if you grow only one lettuce in the tropics, romaine is the sensible choice.
How do I stop romaine bolting?
Sow only in the coolest months, give plants afternoon shade, water evenly and harvest young. Bolting is triggered by heat and long days, so once the weather warms there is no way to hold a romaine plant back — succession sow instead.
What soil and spacing do romaine lettuce need?
It needs full sun, soil pH 6.0–7.0, and spacing of 8–12 inches between plants. Work compost into the bed before planting and test the soil rather than guessing the pH.