Collard greens are one of the toughest leafy vegetables you can grow, and in Zone 12 they are a solid cool-season choice — tougher and more heat-tolerant than most brassicas, though they still prefer the mildest months. They produce big, nutritious leaves for months if you pick them regularly, and they cope with tropical conditions better than cabbage or broccoli. This guide tells you exactly how to grow them: when to sow, how to start seed, what soil and spacing collard greens need, how to water them, which neighbours help, which pests to watch, and when to harvest. Zone 12 is frost-free, with average winter lows of 50 to 60°F, so there is no last or first frost date to plan around — here you plant by heat and by the wet and dry seasons, not by frost. See the full planting calendar for the whole year, and check your local extension service for advice specific to your area.
Collard Greens at a glance in Zone 12
All figures below are broad published ranges from standard horticultural references, not exact figures for any variety or garden — they vary by variety, climate and soil. Use them to compare crops and to plan, not as promises.
| Detail | Collard Greens |
|---|---|
| Days to germinate | 7–10 |
| Days to maturity | 60–80 |
| Spacing (inches) | 12–18 |
| Soil pH | 6.0–7.5 |
| Sun | full sun |
| Sowing method | both |
| Cold tolerance | frost-tolerant |
| Water needs | moderate |
When to plant collard greens in Zone 12
Sow collard greens at the start of the coolest months, roughly December in most Zone 12 areas, so they have the longest possible mild run. The published maturity range is 60–80 days, which fits the cool season well, and the plants keep producing leaves for weeks after that. Collards are more heat-tolerant than most brassicas, so they may keep going into the warm season if you give them afternoon shade and steady water — but the leaves will get tougher and more bitter as temperatures climb. Because the zone is frost-free, with winter lows of 50 to 60°F, there is no frost date to count from — sow by temperature, and check your local extension service for advice specific to your area. Our December in Zone 12 guide shows what else to sow that month.
Starting collard greens
Start collard greens indoors or sow directly: germination takes 7–10 days and seedlings are quick and vigorous. Sow in individual pots or modules, or direct in the bed, and thin to the strongest plants. Space plants 12–18 inches apart — they grow large and need room for air to circulate. Transplant carefully and water in well, or sow direct and thin once seedlings are a few inches tall. The watering calculator helps you plan how much water a bed of leafy greens needs in the dry season. Collards are forgiving of a rough start, which makes them a good first brassica.
Soil, spacing and sun
Collard greens need rich, well-drained soil with a soil pH of 6.0–7.5. Dig in plenty of well-rotted compost or aged manure before planting, since collards are hungry feeders. Good drainage matters in tropical wet seasons, so a raised bed is the safest choice. Full sun suits collards in the cool season, but in Zone 12 a spot with afternoon shade helps during hot spells and keeps the leaves tender. Mulch thickly to hold moisture and keep the soil cool. Feed lightly through the season with compost or a balanced liquid feed, since regular picking removes a lot of nutrients.
Watering and feeding
Collard greens need moderate, steady water. Keep the soil evenly moist from planting to harvest — dry spells make leaves tough, bitter and quick to bolt. Water at the base in the morning, and mulch thickly to slow evaporation in tropical sun. In the dry season, a deep soak once or twice a week is better than daily sprinkles. Avoid wetting the leaves late in the day, since damp foliage in humid air invites disease. As the weather warms, extra mulch and shade can keep the plants producing for several more weeks.
Companion planting
Good companions for collard greens are marigolds, basil, onions and lettuce. Onions are useful neighbours that may help confuse cabbage pests. Lettuce can fill the gaps between young plants and shades the soil. Marigolds at the bed edges may help with soil pests. Avoid planting collards next to other brassicas in the same season, since they share pests, and do not follow any brassica with another brassica in the same bed — rotate to a different family next season. For another leafy green from the same season, see our guide to Mustard Greens in Zone 12.
Pests and problems
Watch for cabbage worms, aphids, flea beetles and slugs. Cabbage worms are the main threat: the small white butterflies lay eggs on the leaves and the green caterpillars chew holes. Cover plants with fine insect mesh from planting, and check the undersides of leaves weekly, picking off caterpillars by hand. Aphids cluster on tender growth and can be washed off with water. Flea beetles pepper young leaves with small holes — mesh helps here too. Slugs hide in the damp shade at the base; check at night and remove them by hand.
Harvest and storage
Harvest collard greens by picking the outer leaves as needed, working from the outside in, usually from within the published maturity range of 60–80 days from sowing. The plant keeps producing new leaves from the centre for weeks or months, so you can harvest little and often. Pick leaves when they are large but still tender — older leaves get tough and bitter, especially in warm weather. Wash well, remove the tough stems, and cook the leaves; collards are best cooked, in soups, stews or sautéed with garlic. Store picked leaves in the fridge for a few days.
Frequently asked questions
Are collard greens good for Zone 12?
Yes — they are one of the better brassicas for Zone 12. They are tougher and more heat-tolerant than cabbage or broccoli, and they keep producing leaves for weeks. Sow in the coolest months.
How do I harvest collard greens?
Pick the outer leaves as needed, working from the outside in. The plant keeps producing new leaves from the centre, so you can harvest little and often for weeks.
Why are my collard leaves bitter?
Usually heat or drought. Collards get bitter in hot, dry weather. Water steadily, mulch thickly, give afternoon shade, and pick leaves while they are young and tender.
How do I stop cabbage worms?
Cover plants with fine insect mesh from the day you plant them out, and check leaf undersides weekly for caterpillars. Mesh is far more reliable than spraying in a tropical garden.