Vegetable · Brassicaceae
Kohlrabi
Brassica oleracea Gongylodes Group
Grown fast and cool and gathered small, kohlrabi brings a crisp, sweet bulb from bed to table.
Full sun
Every 3–7 days
64–75°F · 18–24°C
45–60 days
Overview
Kohlrabi has a quiet charm in the spring bed, a pale or purple globe resting on the soil with leaves fanning out above it. It belongs to the cabbage family, the same species as broccoli, kale, and cabbage, simply coaxed to thicken its stem instead of a head or a spray of leaves. On the plate it reads as a mild turnip meeting a broccoli stem, crisp and lightly sweet, a fresh note for early-season menus.
This is a cool-season crop that suits the gentle rhythm of spring and fall gardening. It comes to size quickly, often in well under two months, which lets it fold neatly into a kitchen garden that turns over twice a year. Timing carries the whole affair: a bulb grown quickly and gathered young stays tender for the table, while one held too long through heat drifts toward tough and bitter.
It rewards the gardener working with a modest plot or a busy week. The plants keep to a small footprint, take a light frost in stride, and ask only for steady water and honest soil. Set the timing well and the bed delivers crisp bulbs that slip easily into a daily cooking routine.
Care
The short version: full sun and cool weather, steady moisture of about an inch of water a week to keep the bulbs tender, a rich and well-drained soil, and a harvest gathered young at 2 to 3 inches across.
Light
Give kohlrabi full sun, at least six hours a day, for the most even growth in the bed. It accepts partial shade in hot weather, a genuine grace in high summer, since the cooler light keeps the plants composed and slows them before they bolt.
Water
Aim for even, consistent moisture, about an inch of water a week, the quiet detail that shapes a good bulb. Steady water builds tender, mild stems, while a plant left to dry and then recover turns tough, woody, and bitter.
Soil
Set it in loamy, well-drained soil enriched with plenty of organic matter. A pH of 6.0 to 7.5 suits it, and leaning toward the higher end offers a measure of protection against clubroot, the disease that shadows the cabbage family.
Temperature
Kohlrabi is at its best in cool air between 64°F and 75°F (18°C to 24°C). A light frost passes without incident, but heat is the discourtesy it cannot abide, as warm spells hurry it into bolting and leave the bulbs tough.
Humidity
Ordinary outdoor humidity carries it along, so there is no figure to fuss over. The detail that truly matters is steady soil moisture, the thing that keeps the bulbs crisp for the kitchen.
Feeding
Work a balanced or low-phosphorus fertilizer into the bed at planting, guided by a soil test where one is at hand. A side-dressing of nitrogen once the plants reach about 4 inches tall keeps their growth on pace.
Pruning
Kohlrabi calls for no pruning whatsoever. The only leaves to remove are lower ones gone ragged from pests or disease, which are best pulled and discarded rather than left to linger on the plant.
Size & spacing
The plants keep a tidy scale, standing just 6 to 12 inches (15 to 30 cm) tall and about as wide. Space the standard varieties near 4 inches (10 cm) apart, giving each the room to round out its bulb without crowding the row.
When to plant
Kohlrabi keeps company with the cooler seasons and shrinks from summer heat. Sow it in early spring for a late-spring harvest, then sow again in July so the bulbs come in with the cool of fall. Each planting rounds out in well under two months.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: early spring, 4 to 6 weeks before transplanting outdoors
- Plant: mid-April to early May for spring crop, or July for fall crop
- Harvest: harvest when the swollen stem reaches 2 to 3 inches in diameter
Hardiness
USDA hardiness zones: 3–9
Temperature: down to -40°C
Troubleshooting
Most of what troubles kohlrabi comes down to timing and the cabbage-family pests it shares with its relatives. Noticed early, they settle easily. Match what appears in the bed below, then step in before the bulb or the leaves lose their promise.
Wilting, stalled plants in the bed
A plant that wilts and refuses to fill out is telling a story below the soil. Lift it to find the tunnels of cabbage maggots or the swollen, club-shaped galls of clubroot. Nothing revives an infected plant, so remove and destroy it, then keep the brassicas circulating through the beds on a four-year rotation and hold the soil pH toward the higher end to keep clubroot at bay.
Fix:
- Remove and destroy affected plants
- Practice a 4-year rotation away from brassicas
Bulbs turned woody and bitter at the table
A bulb loses its kitchen appeal when it grows too large, so the remedy is to gather it earlier for the plate. Slice one and a stringy interior confirms it lingered in the bed too long or endured a spell of heat and drought. Lift them at 2 to 3 inches (5 to 8 cm) across and keep the soil evenly moist, and every one arrives crisp and sweet.
Fix:
- Harvest at 2 to 3 inches in diameter for best quality
- Keep soil evenly moist to maintain fast, uninterrupted growth
Ragged holes marring the leaves
Green caterpillars spoil the tidy look of the foliage, most often imported cabbageworms, cabbage loopers, or diamondback moth larvae. Turn a leaf and they appear, quietly at work beside dark specks of frass. A little handpicking, a pass of Bt where it suits the plot, and a floating row cover set over young plants keeps the moths away and the bed looking its best.
Fix:
- Handpick caterpillars
- Apply Bacillus thuringiensis (Bt) where appropriate
- Use floating row covers
Fine shot-holes dotting the young leaves
The delicate pinholes come courtesy of flea beetles, which scatter the instant a hand nears the plant. On a young seedling the effect looks worse than it is, and a healthy plant carries on unbothered. Draped over the bed at planting, a row cover keeps them out, and a well-fed plant simply grows past the blemishes.
Fix:
- Use floating row covers at planting
- Maintain vigorous growth so plants outgrow damage
Toxicity
Kohlrabi is wholly safe, a food crop that carries nothing harmful for people or animals. The bulb and the leaves are both edible, so a curious pet taking a nibble is nothing to trouble over. The only note of caution is quantity, since any brassica can bring on gas, and a large feed is best kept from horses.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Around cats, kohlrabi sits easily in the home, safe and untroubling. A passing nibble of leaf or stem does no harm, even if it rarely tempts a cat in the first place.
Dogs None
A dog can share in kohlrabi with no concern, a plain raw or cooked piece slipped in as a treat. A generous portion may bring a little gas, and that is the extent of it.
Horses Mild
For a horse, a modest taste is fine, though a large feed of any brassica can unsettle digestion or, over time, touch the thyroid. It belongs on the occasional-treat list, nothing more.
Rabbits Safe
Rabbits take gladly to both the leaves and the bulb. A slow introduction in modest portions lets the gut settle into a new green with ease.
Livestock Safe
Cattle, goats, and sheep graze kohlrabi safely. As with any brassica, easing it into the diet gradually rather than all at once keeps everything comfortable.
Birds Safe
Backyard hens and other birds peck contentedly at the leaves and stem. The plant holds nothing that puts them at risk.
People Safe
Kohlrabi is grown for the table, enjoyed raw or cooked by every age. The crisp bulb and the leafy tops alike make fine eating.
As a brassica, large quantities can cause gas or mild goitrogenic effects; horses should not be fed large amounts.
Varieties
Only a handful of kohlrabi varieties turn up in most seed catalogs, sorted chiefly by color and size. These are the ones worth keeping in mind when planning a bed.
Purple Vienna
An heirloom that dresses pale greenish-white flesh in a coat of deep purple skin.
White Vienna
The familiar pale green form, quietly prized for flesh that is crisp and mild.
Kossak
A generous storage variety that keeps its tender character at a size well beyond ordinary kohlrabi.
How to propagate
Kohlrabi comes from seed alone, and it makes one of the more effortless additions to a spring sowing plan.
SeedEasy
Sow indoors in early spring 4 to 6 weeks before transplanting, or direct sow mid-April to early May and again in July for fall · 7 to 14 days to germinate, with bulbs ready 45 to 60 days from sowing
Kohlrabi arrives from seed with a quiet, obliging ease. Start it indoors in early spring some 4 to 6 weeks ahead of transplanting, or sow it straight into the bed from mid-April through early May, then once more in July for a crop that ripens into fall. Settle each seed 1/4 to 1/2 inches (5 cm) deep and thin the standard plants to 4 inches (10 cm) apart. Green appears in 7 to 14 days, and the bulbs are ready for the table 45 to 60 days from sowing.
Myths
Kohlrabi is a root vegetable like a turnip.
The part that reaches the kitchen grows above the soil, never beneath it. That rounded globe is a swollen stem, rising from the base of the plant rather than delving downward as a root. The old name German turnip only muddies matters, since kohlrabi is a brassica, a far nearer relation to cabbage than to any true turnip.