USDA Zone 11 is frost-free year-round, with average winter lows of 40 to 50°F. There is no last spring frost and no first autumn frost to plan around, so Zone 11 gardeners plant by heat and by the wet and dry seasons instead of by frost dates. The heat and humidity that let tropical crops grow all year make cool-season crops much harder. Frost dates here are zone averages and vary by microclimate, elevation and year — check your local extension service for guidance for your exact spot.
Kohlrabi is the brassica that looks like a vegetable from another planet — a swollen, round stem that tastes like a mild cross between cabbage and broccoli stem. In Zone 11 it is strictly a cool-season crop: it matures in 50–60 days, which is fast enough to fit inside the short cool window, but it bolts and turns woody fast once real heat arrives, so timing is everything.
Zone 11 at a glance
USDA Zone 11 is frost-free year-round, with average winter lows of 40 to 50°F. Plant by the season: the coolest, driest months for cool-season crops, and the cooler part of the year for the best fruit set on heat lovers.
| Detail | Zone 11 guidance |
|---|---|
| Average winter low | 40 to 50°F |
| Last spring frost | None — frost-free year-round |
| First autumn frost | None — frost-free year-round |
| Days to germination | 7–10 days |
| Days to maturity | 50–60 days |
| Sowing | both |
| Best planting window | November to February (coolest months); sow in succession every 2–3 weeks |
| Harvest | 50–60 days after sowing/transplanting |
| Sun | full sun |
| Soil pH | 6.0–7.5 |
| Spacing | 6–9 inches |
| Water needs | moderate |
| Cold tolerance | frost-tolerant |
When to plant kohlrabi in Zone 11
Sow kohlrabi from November through February, when Zone 11 is at its coolest, and sow a small batch every two to three weeks rather than everything at once — staggered sowings give a steady harvest instead of twenty stems ripening in one hot week. Seeds germinate in 7–10 days. Because the crop takes only 50–60 days to mature, a sowing made in early February can still be picked before the heat builds. Do not try a spring or summer sowing: plants will bolt, the stems will turn tough and woody, and you will get leaves instead of a harvest.
Work by the season rather than by frost dates: the planting calendar hub gives the Zone 11 picture month by month, and the month guide for November in Zone 11 shows what else is happening at planting time. The harvest date calculator can turn your sowing date into a harvest window.
Starting kohlrabi in Zone 11
Kohlrabi can be started indoors or sown directly outdoors, and in Zone 11 direct sowing in the cool months usually works well. Sow seed about a quarter to a half inch deep in seed-starting mix or prepared bed soil, keep it evenly moist, and thin seedlings to their final spacing once they have a few true leaves — crowded kohlrabi stays small. If you start indoors, transplant seedlings out when they are sturdy and have three or four true leaves, and harden them off for several days first, moving them into shade and then sun so the move outdoors does not check their growth.
Soil, spacing, sun and water
Kohlrabi grows best in full sun, in soil with a pH of 6.0–7.5, spaced 6–9 inches apart. Kohlrabi wants rich, moisture-retentive soil that still drains well, and even watering matters more for this crop than for most: a dry spell followed by heavy watering can split the swollen stem, and drought stress makes it woody. Dig in well-rotted compost before planting and mulch to hold moisture steady through the cool season. Kohlrabi needs moderate water: water deeply when the top inch or two of soil feels dry, rather than sprinkling lightly every day, and water at the base in the morning so leaves dry before night. Mulch helps hold moisture.
Companion planting
Good companions for kohlrabi include marigolds, basil, onions, lettuce. The companion planting finder can suggest combinations for your whole garden. Rotate crops each year and avoid planting where the same family (Brassicaceae) grew last year. A related crop to plan alongside is rutabaga, which shares the Zone 11 calendar, so the two guides work well together.
Pests and problems
The common pests and problems to watch for with kohlrabi are cabbage worms, aphids, flea beetles, slugs. In Zone 11's humid air, slugs are active all year and love young brassica leaves, so check under leaves and mulch in the morning. Cabbage worms chew ragged holes in the foliage; hand-pick caterpillars and look for the tiny white butterflies laying eggs on the leaves. Flea beetles pepper seedlings with small shot-holes, and aphids cluster on tender new growth — a strong jet of water knocks them off before they build up. Inspect plants regularly, especially leaf undersides, and act early: hand-pick larger pests, wash aphids off with water, and remove badly affected leaves. Healthy plants in the right soil and spacing resist pests better than stressed ones. If you are unsure what you are looking at, the pest identifier helper can narrow it down.
Harvest and storage
Harvest kohlrabi when the swollen stem is about the size of a golf ball to a tennis ball — young stems are crisp, sweet and tender, while oversized ones turn fibrous and woody, so do not wait for a giant. Cut the stem at the base, trim the leaves (young leaves are edible cooked like greens), and use the stem peeled, raw or cooked. Kohlrabi keeps for a week or two in the refrigerator in a bag, and it is best used fresh rather than stored long.
Frequently asked questions
When should I plant kohlrabi in Zone 11?
Sow from November through February, in succession every two to three weeks. Zone 11 is frost-free year-round, so the planting window is set by heat, not frost — and kohlrabi bolts in heat. Check your local extension service for your area.
How long does kohlrabi take to grow in Zone 11?
Seeds germinate in 7–10 days and the crop matures in 50–60 days. That short season is what makes it possible in Zone 11 at all, as long as you sow inside the coolest months.
What soil and spacing does kohlrabi need in Zone 11?
It grows best in full sun, in soil with a pH of 6.0–7.5, spaced 6–9 inches apart. Keep water even — dry spells followed by soaking can split the stem — and dig in compost before planting.
What should I plant with kohlrabi in Zone 11?
Good companions include marigolds, basil, onions and lettuce. Rotate brassicas each year and avoid planting where the same family (Brassicaceae) grew last season.