Vegetable · Brassicaceae
Kohlrabi
Brassica oleracea Gongylodes Group
Grow it fast and cool, pull it small, and kohlrabi pays you back with a crisp, sweet bulb perched right on the soil.
Full sun
Every 3–7 days
64–75°F · 18–24°C
45–60 days
Overview
Kohlrabi turns heads in the garden, a pale or purple globe perched on the soil with leaves shooting straight up out of it. It runs in the cabbage family, the same species as broccoli, kale, and cabbage, just steered to swell its stem instead of a head or a leaf pile. Bite it raw and it lands between a mild turnip and a broccoli stem, crisp with a clean little edge of sweetness that makes it a joy to grow and eat.
This is a cool-season crop that hits its stride through the mild days of spring and fall. It races to maturity, often in well under two months, so plenty of gardeners cram two crops into a single year. Speed drives the whole show: a bulb that grows fast and gets picked young stays tender and sweet, while one that slogs through heat or overstays turns tough and bitter.
It delivers a fast, satisfying win for anyone short on time or space. The plants stay small, laugh off a light frost, and want little more than steady water and honest soil. Nail the timing and you pull crisp bulbs with barely any effort, and that quick payoff keeps you coming back for more.
Care
The short version: full sun and cool weather, steady water at about an inch a week to keep the bulbs tender, rich well-drained soil, and a fast harvest pulled young at 2 to 3 inches across.
Light
Hand kohlrabi full sun, at least six hours a day, and it powers along at a steady clip. It also takes partial shade in hot weather, a real bonus in summer, since the shade keeps the plants cool and reins them in before they bolt.
Water
Chase even, consistent moisture, about an inch of water a week, because this drives bulb quality more than anything else. Steady water grows tender, mild stems, while a plant that dries out and rebounds turns tough, woody, and bitter.
Soil
Sink it into loamy, well-drained soil loaded with organic matter. A pH of 6.0 to 7.5 hits the sweet spot, and pushing toward the higher end helps beat back clubroot, the disease that stalks the cabbage family.
Temperature
Kohlrabi charges ahead in cool air between 64°F and 75°F (18°C to 24°C). A light frost barely fazes it, but heat is the real enemy, since warm spells shove it into bolting and leave the bulbs tough.
Humidity
Plain outdoor humidity covers it, so skip chasing any figure. What truly counts is steady soil moisture, and that is what keeps the bulbs crisp.
Feeding
Fold a balanced or low-phosphorus fertilizer into the bed at planting, guided by a soil test where you can swing it. Side-dress a shot of nitrogen once the plants top about 4 inches tall to keep them charging along.
Pruning
Kohlrabi wants no pruning whatsoever. The only leaves you strip off are the lower ones that go ragged from pests or disease, and those get pulled and tossed instead of left on the plant.
Size & spacing
These plants keep it compact, topping out at just 6 to 12 inches (15 to 30 cm) tall and about as wide. Space standard varieties around 4 inches (10 cm) apart so each one has room to bulk up its bulb without crowding.
When to plant
Kohlrabi thrives in cool weather and wilts at the thought of summer heat. Sow it in early spring for a late-spring harvest, then fire off another sowing in July so the bulbs finish in the cool of fall. Each crop races to the finish 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 kohlrabi hiccups trace back to timing and the cabbage-family pests it shares with its cousins. Jump on them early and they fold fast. Match what you spot below, then move before the bulb or the leaves take any real hit.
Wilting, stalled plants with root damage
A plant that wilts and quits growing for no clear reason is hiding trouble below the surface. Dig it up and hunt for the tunnels of cabbage maggots or the swollen, club-shaped galls of clubroot. An infected plant is a lost cause, so yank it and destroy it, then keep brassicas moving on a four-year rotation and hold the soil pH up to shut clubroot down.
Fix:
- Remove and destroy affected plants
- Practice a 4-year rotation away from brassicas
Bulbs gone tough and bitter
A woody bulb almost always means it grew too big, so grab the next one earlier and the problem disappears. Slice one open and a stringy inside gives it away: it lingered too long or battled through heat and drought. Pull them at 2 to 3 inches (5 to 8 cm) across, keep the soil evenly moist, and the stems come out crisp and sweet every time.
Fix:
- Harvest at 2 to 3 inches in diameter for best quality
- Keep soil evenly moist to maintain fast, uninterrupted growth
Ragged holes chewed through the leaves
Green caterpillars are chewing away here, usually imported cabbageworms, cabbage loopers, or diamondback moth larvae. Flip a leaf and there they are, munching next to dark specks of frass. Pick them off, hit them with Bt where it fits, and throw a floating row cover over young plants to lock the moths out before they ever lay.
Fix:
- Handpick caterpillars
- Apply Bacillus thuringiensis (Bt) where appropriate
- Use floating row covers
Tiny shot-holes across the young leaves
Those little pinholes shout flea beetles, which spring off the moment a hand comes near. It looks rough on a seedling, sure, but a strong plant powers right through it. Snap a row cover over the bed at planting, keep the plants well fed, and they blast past the damage in no time.
Fix:
- Use floating row covers at planting
- Maintain vigorous growth so plants outgrow damage
Toxicity
Kohlrabi is completely safe, a food crop with nothing toxic in it for people or animals. Both the bulb and the leaves are edible, so a curious pet grabbing a nibble is no drama at all. The one thing to watch is quantity, since any brassica can bring on gas, and a big feed is not the move for horses.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Cats are in the clear with kohlrabi. A curious nibble of leaf or stem does nothing at all, even if most cats stroll right past it.
Dogs None
Dogs can dig into kohlrabi with zero worries, raw or plainly cooked. Toss them a plain piece as a treat and expect nothing worse than a bit of gas from a big helping.
Horses Mild
A small taste sits fine with a horse, but a big feed of any brassica can churn up the gut or, over time, nudge the thyroid. Hand it over as an occasional treat and all stays well.
Rabbits Safe
Rabbits happily chomp both the leaves and the bulb. Bring it in slowly and in small portions so their gut eases into a fresh green.
Livestock Safe
Cattle, goats, and sheep graze kohlrabi safely. Like any brassica, work it into the diet bit by bit rather than dumping it in all at once.
Birds Safe
Backyard hens and other birds peck away happily at the leaves and stem. Nothing in the plant can hurt them one bit.
People Safe
Kohlrabi is grown to be eaten, raw or cooked, by people of every age. The crisp bulb and the leafy tops both make great food.
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 land in most seed catalogs, sorted mostly by color and size. Here are the standouts worth grabbing.
Purple Vienna
An heirloom that flashes deep purple skin over pale greenish-white flesh.
White Vienna
The go-to pale green type that growers reach for thanks to its crisp, mild flesh.
Kossak
A giant storage variety that holds its tender bite even after it bulks up well past standard kohlrabi.
How to propagate
Kohlrabi grows from seed and nothing else, and it ranks among the easiest, most rewarding seeds you can start.
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 rockets up from seed and barely asks for a thing. Kick it off indoors in early spring around 4 to 6 weeks before transplanting, or drop seed straight into the ground from mid-April through early May, then again in July for a fall run. Tuck each seed 1/4 to 1/2 inches (5 cm) deep and thin standard plants to 4 inches (10 cm) apart. Sprouts push up in 7 to 14 days, and the bulbs are ready to pull 45 to 60 days after sowing.
Myths
Kohlrabi is a root vegetable like a turnip.
Here is the fun part: the part you eat rises above the soil, not down in it. That round globe is a swollen stem that bulges out from the base of the plant instead of drilling downward like a root. And that old name German turnip throws everyone off, because kohlrabi is a brassica through and through, far closer to cabbage than to any true turnip.