Scallions are the quickest allium in the Zone 10 garden: sow seed in autumn and pull slim, mild green onions within two months. They take up almost no space, grow in gaps between slower crops, and can be sown again and again through the long cool season.
Zone 10 at a glance
USDA Zone 10 covers the warmest parts of the United States, including southern Florida, the southern tip of Texas, coastal southern California and Hawaii. Winters are mild, with average winter lows of 30 to 40°F, and the growing season runs nearly all year — frost is rare rather than a regular event.
The average last spring frost in Zone 10 is Jan 15–30 (frost rare), and the average first autumn frost is Dec 15–31 (frost rare). These are zone averages drawn from NOAA frost records, not exact dates for any one garden — always check your local extension service and the forecast before planting tender crops outside. Frost dates vary by microclimate, elevation and year, so treat them as a guide, not a promise. Use our frost date calculator for your zone's averages.
When to plant scallions in Zone 10
Plant scallions from October to April in Zone 10, sowing seed directly every few weeks for a continuous supply. Scallions are hardy and grow best in cool weather; they mature 60–70 days after sowing, so the long Zone 10 cool season allows many successive sowings. In summer heat they bolt and turn tough, so treat them as a cool-season crop. Because Zone 10 has a long, nearly year-round growing season, the question is rarely whether scallions will grow, but whether you plant them in the right season — heat lovers go in after the last frost, cool-season crops go in for autumn and winter.
Scallions planting at a glance
| Detail | Zone 10 guidance |
|---|---|
| Best planting window | October to April |
| Start indoors | Not needed — direct sow |
| Days to germination | 7–14 |
| Days to maturity | 60–70 |
| Spacing | 2–3 in |
| Soil pH | 6.0–7.0 |
| Sun | full sun |
| Water needs | moderate |
| Cold tolerance | hardy |
All figures are broad published ranges from standard horticultural references, and they vary by variety, soil and weather. Check your local extension service for advice on your own garden.
Starting scallions
Sow scallions directly — they dislike transplanting and are easiest sown in place. Sow seed thinly about a quarter inch deep in rows, and thin seedlings to their final spacing once they are a few inches tall; the thinnings can be eaten. Seed germinates in 7–14 days. Keep the seed bed damp until seedlings emerge. Sow a short row every two to three weeks rather than a whole bed at once, so stems are always young and tender.
Soil, spacing and sun
Scallions need full sun and fertile, well-drained soil with a pH of 6.0–7.0. Work in compost before sowing; scallions are shallow-rooted and need the nutrients close to the surface. Space plants 2–3 inches apart in rows — they need very little room, which is why they are ideal for edging beds and filling gaps. In Zone 10's sandy soils, compost and mulch hold the moisture shallow roots depend on. Good drainage matters: scallions hate sitting in wet soil.
Watering and feeding
Scallions have moderate water needs and grow best with even moisture: dry plants turn tough and strong-flavoured, while well-watered plants stay mild and crisp. Water little and often, keeping the top few inches of soil damp. In Zone 10's dry, sunny winters, a shallow-rooted crop like scallions dries out fast, so check the bed every couple of days. Mulch lightly to hold moisture, but keep it away from the stems.
Companion planting
Good companions for scallions are marigolds, basil, onions and lettuce. Scallions are the classic gap-filler: sow them along the edges of beds and between slow crops such as leeks and carrots, where they use space that would otherwise be wasted. Their scent is said to deter aphids and carrot fly. Avoid planting scallions near peas and beans, which grow poorly alongside alliums, and rotate alliums to fresh ground each year.
Pests and problems
The pests to watch for are aphids, slugs and cutworms. Aphids cluster on young leaves and can be washed off with water. Slugs nibble seedlings on damp nights. Onion fly can attack in some areas; insect netting over the bed from sowing keeps flies off. Because scallions grow fast and are picked young, pest pressure rarely becomes serious, and the crop is usually harvested before problems build.
Harvesting and storing scallions
Harvest scallions when the stems are pencil-thick, 60–70 days after sowing — pull the whole plant, roots and all, once it reaches the size you want. Young, thin scallions are milder; thicker ones are stronger. Pull gently after watering, so the soil releases the roots, and trim the roots and the very tip of the green tops. Scallions are best used fresh within a few days, though they keep for a week in the fridge in a damp cloth or bag.
Frequently asked questions
When do I plant scallions in Zone 10?
From October to April, sown directly every few weeks. They are a cool-season crop — check your local extension service for the best dates in your area.
What is the difference between scallions and green onions?
In the garden they are much the same: scallions are onions harvested young, before a bulb forms. Any onion variety can be grown as scallions if pulled young.
Why are my scallions tough and strong?
Usually heat or drought. Scallions need cool weather and even moisture; sow in the cool months and water little and often.
How long do scallions take to grow in Zone 10?
Seed germinates in 7–14 days and stems are ready in 60–70 days.
For the full year, browse the planting calendar hub. Nearby: january in Zone 10, Scallions in Zone 9 and Leeks in Zone 10. Use the germination time calculator and the seed spacing calculator to plan your own dates.