How to Grow Kohlrabi

What Kohlrabi Is and Why It's Easy

Kohlrabi is a cole crop, the same species group as cabbage, broccoli, and kale, but instead of a head or florets you eat the round, swollen stem that forms just above the soil line. The flavor is mild, sweet, and crisp, somewhere between cabbage heart and broccoli stem, and it can be eaten raw or cooked.

Because you are harvesting a young stem rather than waiting for fruit or a mature head, kohlrabi is one of the fastest brassicas in the garden. Utah State University Extension lists varieties maturing in as little as 40 days and up to about 60 days, which makes it a natural crop for succession sowing and for squeezing into shoulder seasons.

When to Plant

Kohlrabi is a cool-season crop that performs best when temperatures stay below 75 F, according to Utah State University Extension. USU advises planting seed or setting out transplants 1 to 2 weeks before the average last spring frost. Young plants can be damaged by hard frosts, so light frost protection is worthwhile if a cold snap threatens after planting.

University of Minnesota Extension recommends direct seeding in the garden from mid-April until early May for a spring crop, and again in July for a fall crop that matures in cooling weather. If you start transplants indoors, USU notes it generally takes 5 to 6 weeks to grow a transplant with 4 to 6 mature leaves and a well-developed root system.

One quirk worth knowing: kohlrabi can bolt (flower prematurely) if it experiences too much cold. USU notes mature plants will flower if average temperatures during growth stay below 45 F, so avoid setting large transplants out during extended cold spells.

✔ Fast, steady growth without heat or moisture stress is the whole game with kohlrabi - stressed plants make tough, woody bulbs.

Sun, Soil, and Spacing

Give kohlrabi a sunny location. University of Minnesota Extension recommends loamy, well-drained soil high in organic matter with a pH of 6.0 to 7.5, improved with well-rotted manure or compost worked in during spring or fall.

Utah State University Extension's planting figures: sow seed 1/4 to 1/2 inch deep, and space seeded or transplanted kohlrabi 6 inches apart in the row with rows 1 foot apart. If you direct-seed thickly, thin seedlings once they have 3 to 4 true leaves.

Rotation matters for all brassicas. UMN Extension advises not planting kohlrabi where related crops - broccoli, cauliflower, cabbage, kale, collards, turnip, rutabaga, mustard, bok choy, or Brussels sprouts - have grown in the previous four years, to limit shared soilborne diseases and pests.

Watering and Feeding

Utah State University Extension recommends 1 to 2 inches of water per week for kohlrabi. Keep moisture even; drought stress slows growth and pushes bulbs toward woodiness and bitterness.

For fertility, USU suggests side-dressing with a nitrogen fertilizer (about 1/2 cup of 21-0-0 per 10 feet of row) roughly 3 weeks after transplanting. Mulch helps hold soil moisture - USU suggests applying organic mulches once temperatures climb above 80 F, or using plastic mulch earlier in the season.

Harvesting

Harvest kohlrabi when the swollen stem reaches 2 to 3 inches in diameter - both Utah State and Minnesota Extension agree on this window. Cut the plant at the soil line, then trim off the leaf stems. Do not wait for a bigger bulb: oversized kohlrabi becomes tough, woody, and bitter.

Depending on variety, expect roughly 40 to 60 days from planting to harvest (USU). Harvested bulbs keep for 2 to 3 weeks stored at 32 F and 95 percent relative humidity, per USU - in practice, a refrigerator crisper drawer in a loosely closed bag.

Common Problems

Kohlrabi shares the standard brassica pest lineup. Utah State University Extension lists aphids, cabbage worms, cabbage loopers, and flea beetles as the main insect problems. Floating row cover placed at planting is a simple, spray-free way to exclude the caterpillar moths and flea beetles from a fast crop like this.

The most common quality problems - woody texture and bitter flavor - are not diseases at all but the result of heat stress, drought stress, or simply harvesting too late. Consistent water and on-time harvest prevent most of them. The four-year rotation away from other cabbage-family crops recommended by UMN Extension is your main defense against soilborne brassica diseases.

Sources

Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.

• Utah State University Extension — How to Grow Kohlrabi in Your Garden — Planting 1-2 weeks before last frost; seed depth 1/4-1/2 inch; spacing 6 inches in rows 1 foot apart; growth best below 75 F; bolting risk below 45 F average; 1-2 inches water/week; 1/2 cup 21-0-0 per 10 ft row 3 weeks after transplanting; 40-60 days to maturity; harvest at 2-3 inch stem diameter; storage 2-3 weeks at 32 F and 95% RH; pests aphids, cabbage worms, loopers, flea beetles.
• University of Minnesota Extension — Growing kohlrabi in home gardens — Direct seed mid-April to early May and again in July; loamy well-drained soil high in organic matter, pH 6.0-7.5; four-year rotation away from related brassica crops; harvest at 2-3 inches; oversized bulbs turn tough, woody, bitter.

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