How to Grow Kohlrabi: The Friendly Alien of the Garden

GardenDraft Team · August 23, 2026 · Updated August 1, 2026 · 8 min read

Part of: Garden Planning Guides · How to Grow Vegetables — Crop Guides A–Z

Kohlrabi is the friendly alien of the vegetable garden — a swollen, knobby bulb that sits right on top of the soil with leaves sprouting out of it like antennae. Odd as it looks, it's one of the easiest and fastest brassicas to grow, with a crisp, mild, sweet flavor somewhere between a cabbage stem and a broccoli stalk. Grow it cool, harvest it young, and it rarely gives any trouble.

What you're actually growing

The edible part isn't a root — it's a swollen stem that bulges into a bulb just above the soil line, which is why kohlrabi doesn't need the deep, loose soil that true root crops do. That makes it forgiving in heavier ground where carrots or parsnips would struggle. Varieties come in pale green and striking purple (the flesh is white inside either way), and they're grown identically.

There's one more split worth knowing from the kohlrabi catalog page: standard quick types, ready in about 45 to 60 days, versus giant storage types, which take closer to 70–90 days, grow softball-size and beyond without going woody, and keep for months in a cold cellar. The quick types are the ones to succession-sow; the giants are a single fall planting you stash for winter.

Cool season, quick crop

Like its cabbage-family cousins, kohlrabi is a cool-season crop that's sweetest and most tender in spring and fall, and it grows fast, with many types ready in about 45 to 60 days. Sow in full sun in rich, evenly moist soil, either direct-sown about a quarter to half an inch deep or from transplants. Thin or space plants about 4 to 6 inches apart so each bulb has room to swell. Steady moisture is the key to crisp, mild bulbs — irregular watering or heat stress makes them woody and can push plants to bolt.

Timing from your frost dates

Kohlrabi's catalog window opens early: direct-sow or transplant from two to four weeks before your last frost through the couple of weeks around it — young plants shrug off light freezes and the crop tolerates temperatures down to the low 20s°F (what your last frost date means). For transplants, sow indoors 4–6 weeks before setting out and give seedlings a week to ten days of hardening off. Then keep going: with the catalog's 14–21 day succession interval, a short fresh row every few weeks yields tennis-ball bulbs continuously until early summer heat calls a pause (succession planting explained).

The fall crop is even better. Count your variety's days to maturity back from your first frost date, add a couple of weeks for slowing autumn growth, and sow in mid-to-late summer — the fall-garden guide does this arithmetic for the whole brassica clan. Fall bulbs sweeten in the chill the way kale does, and the giant types finish best this way.

Spacing, soil, and feeding

In a square-foot bed the standard value is 6 inches — four plants per square — with giant types wanting a full square each. Kohlrabi isn't a deep feeder, but like all leafy brassicas it wants nitrogen early: compost worked in before planting plus one light feed when plants are a few weeks old is usually the whole program (feeding guide). A brassica-bed soil test every few years is worthwhile since clubroot risk climbs in acidic ground; a pH near neutral keeps that door shut. An inch of water a week, delivered evenly, is the difference between crisp and woody — a light mulch smooths out the swings.

The one rule: harvest kohlrabi young

This is what separates good kohlrabi from disappointing kohlrabi — pick the bulbs young, when they're about 2 to 3 inches across, roughly the size of a tennis ball. At that size they're crisp, sweet, and tender right through. Left to grow large they turn woody, fibrous, and pithy in the center, which is the usual reason people decide they don't like kohlrabi. Newer varieties hold their quality at a larger size, but for the classic types, smaller is sweeter. Cut the bulb at the base, peel the tough outer skin, and eat it raw like an apple, grated into slaw, or roasted. Don't toss the leaves: they cook up like any other brassica green.

Trimmed of leaves, bulbs keep several weeks in the refrigerator crisper, and the fall giants hold for months somewhere cold and humid — treat them like the storage roots in this winter-keeping guide.

Few problems

Kohlrabi shares the cabbage family's pests (flea beetles and cabbage worms chiefly) but because it grows so quickly and the edible bulb isn't the part the caterpillars target, it usually sails through with minimal damage. A row cover handles them if needed — drape it at sowing, when flea beetles do their only meaningful damage to the seedlings. Otherwise this is a genuinely low-effort, quick-turnaround crop that's perfect for tucking into gaps.

The failures you do see trace to stress, not pests. All leaves, no bulb means crowding, too much shade, or heat arriving before the stem could swell — thin ruthlessly and time sowings cooler. Split bulbs follow a heavy rain after drought, same as cracking tomatoes; steady water prevents it. Woody bulbs mean the harvest window slipped past. And because it's a brassica, keep kohlrabi in the cabbage slot of your crop rotation so soil diseases never get a foothold. Flea beetles on seedlings are the one early threat worth a row cover in most gardens.

The gap-filler's crop

Kohlrabi's real superpower in a planned garden is scheduling. At four plants per square and six to nine weeks per crop, it slots into the gaps other vegetables leave behind: the square where spring lettuce bolted, the edge of a bed waiting for fall garlic, the strip beside slow-starting peppers that sits empty until July. Interplanting works in the other direction too — kohlrabi matures so fast that a row tucked between young brussels sprouts or other long-season brassicas is harvested before the neighbors need the room (one caveat: all of it counts as cabbage-family ground for rotation purposes). Gardeners who keep a few transplants coming in cells all season, dropping one into every vacancy, quietly pull dozens of bonus bulbs a year out of space that would otherwise have grown weeds.

Kohlrabi in containers

A fast, shallow-rooted, compact crop is a natural for pots: any container 8–10 inches deep grows kohlrabi well at the same 6-inch spacing, four to a 12-inch pot (container-growing basics). Water daily in warm spells — container droughts are what turn pot-grown bulbs woody — and give pots a feed at half strength every couple of weeks, since watering that frequent rinses nutrients out faster than a bed ever loses them. Time your spring and fall sowings on the planting calendar.