Lettuce is the hardest common salad crop in Zone 12, and it is worth saying so plainly: this is a cool-season leaf that bolts — runs to seed and turns bitter — as soon as the weather warms up, and Zone 12, with winter lows of 50 to 60°F, has only a short cool window. Grown in that window, though, lettuce is fast, easy and generous, giving salad leaves in six to eight weeks from a December sowing.
The Zone 12 challenge is heat. These are cool-season crops, and in a frost-free tropical zone the coolest months are short — plant by the coolest part of the year, give afternoon shade, and accept that the season is brief and the harvest smaller than in a cool climate.
Zone 12 at a glance
USDA Zone 12 covers the warmest lowland parts of Hawaii and Puerto Rico. Winters are very mild, with average winter lows of 50 to 60°F, frost is unknown, and the growing season runs all year. Zone 12 has no average last spring frost and no average first autumn frost — it is frost-free year-round — so planting dates here are averages and guidance, not exact dates for any one garden; check your local extension service before planting.
| Detail | Zone 12 guidance |
|---|---|
| Average winter low | 50 to 60°F |
| Average last spring frost | frost-free (no frost dates) |
| Average first autumn frost | frost-free (no frost dates) |
| Days to germination | 7–10 days |
| Days to maturity | 45–60 days |
| Sowing | both |
| Sun | full sun |
| Soil pH | 6.0–7.0 |
| Spacing | 8–12 inches |
| Water needs | moderate |
| Cold tolerance | hardy |
When to plant lettuce in Zone 12
Plant lettuce in Zone 12 in the coolest months only, roughly December through February. Seeds germinate in 7–10 days and the crop matures in 45–60 days, so a sowing made in December is ready around January to February. Zone 12 is frost-free, so there are no last or first frost dates — check your local extension service for advice on your own microclimate. Sown outside the cool window, this crop bolts, turns bitter or fails to size up in the heat, so treat the coolest months as the whole season and plan other crops for the hot months.
The planting calendar hub and the December in Zone 12 month guide show what else is happening at planting time.
Starting lettuce in Zone 12
Lettuce can be sown direct where it is to grow, or started indoors and transplanted as small seedlings. Germination takes 7–10 days, but seed germinates poorly in hot soil, so sow in the coolest months and keep the seed bed damp. Sow little and often — a short row every two weeks through the cool season gives a steady supply instead of a glut that bolts all at once.
See also when to plant lettuce in Zone 11 for the same crop in a slightly cooler zone.
Soil, spacing, sun and water
Lettuce needs rich, moisture-holding, well-drained soil with a pH of 6.0–7.0, and in Zone 12 it needs a spot with morning sun and afternoon shade — full tropical sun is too much for it. Dig in well-rotted compost before sowing, space plants 8–12 inches apart, and mulch lightly to keep the soil cool and moist. They need full sun and a soil pH of 6.0–7.0. Water needs are moderate: water deeply and regularly at the base, in the morning, so leaves dry before night. The seed-starting calculator can help you plan the bed before you plant.
Companion planting
Carrots, radishes, strawberries, cucumbers and onions are good companions for lettuce. Radishes mark the row and are harvested before the lettuce needs the space, carrots use the deeper soil below the lettuce roots, and onions help fill the bed without competing for light. The companion planting finder can suggest combinations for your whole bed, and our guide to when to plant spinach in Zone 12 shows another crop that shares the same planting windows.
Pests and problems
The common pests and problems to watch for with lettuce are aphids, slugs, cutworms. Aphids cluster on soft new growth and leaf undersides; wash them off with a strong jet of water and encourage ladybirds. Slugs feed at night, leaving ragged holes and slime trails; water in the morning and keep the bed clear of debris. Cutworms chew through young stems at soil level overnight; a cardboard collar around each seedling stops them. Your local extension service can confirm an identification if the damage is severe.
Harvest and storage
Pick lettuce as loose leaves from the outside of the plant, or cut a whole head when it feels firm and full. Harvest in the morning when leaves are crisp, and pick promptly — a head left in warming weather bolts within days and turns bitter. Fresh lettuce keeps for several days in the fridge, washed, dried and stored in a bag or box with a little airflow. Pick only what you need, because cut leaves wilt fast in tropical heat.
Frequently asked questions
When should I plant lettuce in Zone 12?
Plant lettuce in Zone 12 in the coolest months only, roughly December through February. Zone 12 is frost-free year-round, so there are no last or first frost dates — plant by the heat and the wet and dry seasons, and check your local extension service for your own microclimate.
Why did my lettuce bolt so fast?
Heat is the cause: lettuce is programmed to run to seed when temperatures rise, and in Zone 12 that can happen within days of a warm spell. Sow only in the coolest months, give afternoon shade, keep the soil moist, and choose heat-tolerant varieties — but even those bolt eventually.
Can I grow lettuce in Zone 12 year-round?
No — not well. This is a cool-season crop, and outside the coolest months, roughly December through February, it bolts, turns bitter or fails to size up in tropical heat. Grow it in the cool window, and plant heat-loving crops in the hot months instead.
Can I grow lettuce in containers in Zone 12?
Yes, and containers are a good option because you can move them into shade during the hottest part of the day. Use a wide, shallow container, rich potting mix, and water daily so the mix stays moist.