Growing kohlrabi in USDA Zone 10 means gardening where winter barely interrupts the year. Zone 10 has average winter lows of 30 to 40°F, an average last spring frost of Jan 15–30 and an average first autumn frost of Dec 15–31 (frost rare), leaving a frost-free stretch of roughly ten to eleven months. Every date below is a zone average — check your local extension service first.
This cool-season crop (Brassicaceae family) takes 50–60 days to maturity and 7–10 days to germinate. In Zone 10 the season is almost always long enough — the question is whether you plant in the right part of the year.
Zone 10 timing for kohlrabi
The table below is the whole plan in one place — check it against the frost date calculator for your area.
| Step | Zone 10 timing |
|---|---|
| Average last spring frost | Jan 15–30 (frost rare) |
| Average first autumn frost | Dec 15–31 (frost rare) |
| Starting method | start indoors or direct sow |
| Sowing window | September to February, sown directly or started indoors |
| Days to germination | 7–10 days |
| Days to maturity | 50–60 days |
| Cold tolerance | frost-tolerant |
When to sow kohlrabi in Zone 10
Kohlrabi is a cool-season brassica in Zone 10, so sow from September to February and let the mild winter do the work. Sow directly or start indoors and transplant, spacing plants 6–9 inches apart. The edible part is the swollen stem above the soil, so keep the soil loose and evenly moist while it swells — a dry spell makes the bulb woody, and uneven watering makes it split. Thin promptly, because crowded plants produce small, tough bulbs.
Nothing tender goes out before the average last frost — keep row cover handy for the first two weeks after transplanting.
Soil, spacing and sun
It needs full sun — at least six hours of direct sun a day. Give it the sunniest spot you have; in Zone 10 the sun is strong even in winter, so most full-sun crops get all the light they need.
Space plants 6–9 inches apart — crowded plants stay small and spread disease faster between touching leaves. Use the plant spacing calculator to work out how many plants fit in your bed.
Soil pH should be in the range 6.0–7.5. Test your soil rather than guessing, work in plenty of compost before planting, and avoid fresh manure, which can burn young roots.
Watering kohlrabi in Zone 10
Water needs are moderate. Water deeply when the top few centimetres of soil are dry — deep watering grows roots downward for hot, dry spells. Mulch holds moisture in and keeps soil temperature steadier.
Water in the morning so leaves dry during the day, and water at the base rather than overhead. In a hot spell, check the soil rather than the calendar.
Companion plants
Good companions for kohlrabi include marigolds, basil, onions, lettuce — the companions listed for this crop in standard horticultural references. Plant companions in the same bed or nearby, and do not follow kohlrabi with another member of the Brassicaceae family in the same bed next year — soil-borne problems build up when the same family is grown in the same place year after year. The companion planting finder can help you check a pairing before you plant it.
Common pests and problems
The common pests to watch for are cabbage worms, aphids, flea beetles, slugs. Check plants at least twice a week — a problem spotted early can be dealt with; spotted late, it may cost you the crop. Look under leaves and at the base of stems, where pests hide. Hand-pick larger pests, wash aphids off with a strong jet of water, and remove badly affected leaves. Row cover keeps many flying pests off young plants. Other problems are usually weather, not pests.
Harvest and storage
Harvest when the swollen stem is a few inches across and still tender, usually 50–60 days after sowing. Do not wait for it to grow as large as possible: an oversized kohlrabi turns woody and fibrous. Pull or cut the plant, trim the leaves and root, and peel the bulb before eating.
Kohlrabi keeps for several weeks in the fridge once the leaves are trimmed off, stored loose in a bag. The leaves are edible too — cook them like other greens and use them fresh, as they do not store as well as the bulb.
Kohlrabi is one of the most forgiving brassicas for a Zone 10 winter garden: it tolerates light frost, grows in a small space, and is ready in under two months. Sow a short row every few weeks in the cool season for a steady supply.
Protection and succession in Zone 10
A cold frame or row cover can save a planting from a rare frost. Succession-sow a second batch two or three weeks after the first, counting the days to maturity against the average first frost in mid-to-late December.
Related Zone 10 guides
If you are planning the whole Zone 10 season, look at the neighbouring guides in this series: Rutabaga in Zone 10 and Kohlrabi in Zone 9, where the season is shorter and the timing shifts. Use the harvest date calculator to work out a harvest window from your sowing date.
Frequently asked questions
When should I plant kohlrabi in Zone 10?
Work from the average last frost of Jan 15–30 and the average first frost of Dec 15–31, both with frost rare: september to February, sown directly or started indoors.
Can kohlrabi survive a frost in Zone 10?
Cold tolerance is frost-tolerant: hardy crops take a light frost, frost-tolerant crops take one once established, and tender crops are killed or badly damaged by frost. Frost is rare in Zone 10, but use row cover on cold nights.
How long does it take to grow in Zone 10?
Germination takes 7–10 days and maturity takes 50–60 days from sowing or transplanting, according to standard published ranges. Warm soil keeps germination near the fast end; cool winter soil can stretch it.
Why is my kohlrabi woody?
Woody bulbs usually come from harvesting too late or from uneven watering. Pick when the swollen stem is still a few inches across, keep the soil consistently moist, and do not leave the plant standing once it reaches size — in Zone 10 warmth it will keep growing and toughen quickly.