Scallions are the fastest allium you can grow, and in Zone 12 they are one of the few onion-family crops that genuinely works. They mature in just 60–70 days, they are harvested young before heat can spoil them, and they grow happily in beds, pots and containers. If you want onion flavour in a tropical garden, scallions are a far safer bet than bulb onions. This guide tells you exactly how to grow them: when to sow, how to start the seed, what soil and spacing scallions 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.
Scallions 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 | Scallions |
|---|---|
| Days to germinate | 7–14 |
| Days to maturity | 60–70 |
| Spacing (inches) | 2–3 |
| Soil pH | 6.0–7.0 |
| Sun | full sun |
| Sowing method | direct sow |
| Cold tolerance | hardy |
| Water needs | moderate |
When to plant scallions in Zone 12
Sow scallions in the coolest months — roughly January in most Zone 12 areas — for the mildest growing weather, but you can also sow them at other times of year if you give them shade and steady water. The published maturity range is only 60–70 days, so scallions fit easily into the cool season, and you can sow small batches every few weeks for a continuous supply. 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 by the wet and dry seasons, and check your local extension service for advice specific to your area. Our January in Zone 12 guide shows what else to sow that month.
Starting scallions
Sow scallion seed directly where it is to grow: germination takes 7–14 days, and the seedlings are thin but quick. Sow shallowly, about a quarter inch deep, in rows or in broad bands, and keep the bed constantly moist until seedlings appear. Thin seedlings to 2–3 inches apart once they are a few inches tall — or leave them closer for thinner, milder scallions. Sow a small batch every two to three weeks for a steady supply rather than one big sowing. The germination time calculator helps you plan succession sowings. Scallions also grow well in pots on a shaded balcony.
Soil, spacing and sun
Scallions need light, fertile, well-drained soil with a soil pH of 6.0–7.0. Dig in well-rotted compost before sowing, and keep the bed weed-free, since scallions have shallow roots and hate competition. Sandy tropical soils suit scallions if they are enriched and kept moist. Full sun is fine in the cool season, but in Zone 12 a spot with afternoon shade keeps the plants tender and slows bolting in hot spells. Mulch lightly between rows to hold moisture and suppress weeds. Feed lightly through the season; scallions are not heavy feeders.
Watering and feeding
Scallions need moderate, steady water. Keep the soil evenly moist from sowing to harvest — dry spells make them tough, hot and quick to bolt. Water gently at the base, ideally in the morning, and mulch to slow evaporation. In the dry season this may mean watering every day or two, especially in pots. Avoid waterlogging, which rots the roots, and avoid wetting the leaves late in the day. Consistent moisture is the key to mild, tender scallions; a single dry spell can turn a whole row pungent and woody.
Companion planting
Good companions for scallions are marigolds, basil, onions and lettuce. Scallions are excellent companions themselves: their scent is said to help deter carrot rust fly and some other pests, so they are worth tucking between rows of carrots and lettuce. Lettuce can fill the gaps and shades the soil. Marigolds at the bed edges may help with soil pests. Avoid planting scallions next to beans or peas, which do not grow well together. Rotate scallions to a fresh bed each year rather than following other alliums. For another allium from the same season, see our guide to Leeks in Zone 12.
Pests and problems
Watch for aphids, slugs and cutworms. Aphids cluster on tender new growth and can be washed off with water. Slugs love damp mulch around scallions — check at night and remove them by hand. Cutworms sever young seedlings at soil level; collars help, and so does keeping the bed clean. Onion fly can attack scallions, so cover young plants with fine insect mesh if it is a problem in your area. The biggest risk in Zone 12 is bolting in heat rather than insects: if flower stalks appear, harvest the whole row at once.
Harvest and storage
Harvest scallions when the stems are pencil-thick and the green tops are fresh, usually within the published maturity range of 60–70 days from sowing. Pull the whole plant, roots and all, or cut the tops and let them regrow once for a second, smaller harvest. In Zone 12, harvest as soon as they are usable — waiting risks bolting and woody stems as temperatures rise. Wash well, trim the roots, and use fresh within a few days; scallions keep best in the fridge in a damp cloth. They are excellent raw in salads, stirred into noodles, or scattered over soups and grilled dishes.
Frequently asked questions
Can scallions grow year-round in Zone 12?
Almost. They mature in just 60–70 days, so they fit any mild spell. Sow in the coolest months for the best results, and give them afternoon shade and steady water in hotter months.
How often should I sow scallions?
Sow a small batch every two to three weeks for a continuous supply. One big sowing gives you a glut followed by nothing — succession sowing is the secret.
Why did my scallions bolt?
Heat is the usual cause. Scallions bolt when temperatures climb, so sow in the coolest months, give them afternoon shade, and harvest as soon as they are pencil-thick.
Can I grow scallions in pots?
Yes — they are ideal for pots and containers. Use a deep pot with rich, well-drained mix, keep it moist, and place it where it gets morning sun and afternoon shade.