Kale is the most heat-tolerant brassica, and that makes it the easiest of the family to grow in Zone 12 — but it is still a cool-season crop, and it does its best work in the coolest months, roughly December through February, maturing in 50–65 days. Unlike cabbage or cauliflower, kale does not need to form a head, so a warm spell that would ruin a cauliflower merely makes kale leaves a little tougher.
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 | 50–65 days |
| Sowing | both |
| Sun | full sun |
| Soil pH | 6.0–7.5 |
| Spacing | 12–18 inches |
| Water needs | moderate |
| Cold tolerance | hardy |
When to plant kale in Zone 12
Plant kale in Zone 12 in the coolest months only, roughly December through February. Seeds germinate in 7–10 days and the crop matures in 50–65 days, so a sowing made in December is ready around February 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 kale in Zone 12
Kale can be sown direct where it is to grow, or started indoors and transplanted out as sturdy seedlings. Germination takes 7–10 days. Sow in the coolest months, space plants 12–18 inches apart, and water seedlings in well — kale is forgiving, but even it grows best from a strong start.
See also when to plant kale in Zone 11 for the same crop in a slightly cooler zone.
Soil, spacing, sun and water
Kale needs full sun and rich, moisture-holding, well-drained soil with a pH of 6.0–7.5, and it tolerates a wider range of soils than most brassicas. Dig in well-rotted compost before sowing, space plants 12–18 inches apart, and mulch to keep roots cool — in Zone 12, light afternoon shade helps kale stay tender. They need full sun and a soil pH of 6.0–7.5. 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
Marigolds, basil, onions and lettuce are good companions for kale. Onions and lettuce fill the ground beneath the tall plants, marigolds edge the bed, and the same companions suit Swiss chard, so the two leafy crops can share a bed plan. The companion planting finder can suggest combinations for your whole bed, and our guide to when to plant swiss chard in Zone 12 shows another crop that shares the same planting windows.
Pests and problems
The common pests and problems to watch for with kale are cabbage worms, aphids, flea beetles, slugs. Cabbage worms are green caterpillars that chew holes in leaves; check leaf undersides and hand-pick, or cover with fine mesh. Aphids cluster on soft new growth and leaf undersides; wash them off with a strong jet of water and encourage ladybirds. Flea beetles chew small holes in leaves, worst on young seedlings; fine mesh row cover and mulching help. Slugs feed at night, leaving ragged holes and slime trails; water in the morning and keep the bed clear of debris. Your local extension service can confirm an identification if the damage is severe.
Harvest and storage
Pick kale leaves from the outside of the plant, starting with the lowest, oldest leaves, and let the centre keep growing — a plant picked this way crops for months. Pick leaves young for tenderness, and harvest in the morning when they are crisp. Fresh kale keeps for about a week in the fridge in a bag. Blanch and freeze surplus leaves, or cook them into soups and stews — kale holds up well to cooking.
Frequently asked questions
When should I plant kale in Zone 12?
Plant kale 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.
Is kale easier than other brassicas in Zone 12?
Yes — kale is the most heat-tolerant brassica, because it is grown for leaves, not a head or curd. A warm spell that makes cauliflower bolt and cabbage split will usually just make kale leaves a little tougher, so it is the best brassica to start with in the tropics.
Can I grow kale 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.
How do I keep kale leaves tender?
Pick leaves young, water evenly, and give afternoon shade in Zone 12 — old, drought-stressed leaves turn tough and bitter. Regular picking also helps: a plant that is picked often keeps producing young, tender leaves.