Vegetable · Brassicaceae
Kohlrabi
Brassica oleracea Gongylodes Group
Grow it fast and cool, pick it while it's small, and kohlrabi gives you a crisp, sweet bulb sitting right on top of the soil.
Full sun
Every 3–7 days
64–75°F · 18–24°C
45–60 days
Overview
Ever seen kohlrabi? It's one of the stranger-looking things you can grow, a pale or purple globe just sitting on the soil with leaves shooting straight out of it. It's part of the cabbage family, actually the same species as broccoli, kale, and cabbage, just bred to fatten its stem instead of making a head or a pile of leaves. Raw, it tastes like a mild turnip crossed with a broccoli stem, crisp with a little sweetness.
It's a cool-season crop, so it does its best work in the mild stretches of spring and fall. It matures quick too, usually in well under two months, which is why a lot of gardeners get two crops out of one year. And speed really is the name of the game here: a bulb that grows fast and gets picked young stays tender, while one that slogs through heat or hangs around too long turns tough and bitter.
If you're tight on time or space, this one's a winner. The plants stay small, they don't mind a light frost, and they don't ask for much beyond steady water and decent soil. Get the timing right and you'll be pulling crisp bulbs without much fuss at all.
Care
The short version: give it full sun and cool weather, keep the water steady at about an inch a week so the bulbs stay tender, plant it in rich, well-drained soil, and pick it young at 2 to 3 inches across.
Light
Give kohlrabi full sun, at least six hours a day, and it'll grow along nice and steady. It's fine with partial shade in hot weather too, which actually comes in handy in summer, since the shade keeps the plants cool and slows them down before they bolt.
Water
Go for even, consistent moisture, about an inch of water a week. This is honestly the biggest thing for bulb quality: steady water grows tender, mild stems, but a plant that dries out and then bounces back? That's what turns them tough, woody, and bitter.
Soil
Get it into loamy, well-drained soil with plenty of organic matter mixed in. A pH of 6.0 to 7.5 works great, and leaning toward the higher end helps keep clubroot at bay, which is the disease that always seems to haunt the cabbage family.
Temperature
Kohlrabi likes it cool, somewhere between 64°F and 75°F (18°C to 24°C). A light frost? No problem. Heat, on the other hand, is the real enemy, because warm spells make it bolt and leave the bulbs tough.
Humidity
Regular outdoor humidity is all it wants, so there's no number to worry about. What really matters is steady soil moisture, and that's what actually keeps the bulbs crisp.
Feeding
Work a balanced or low-phosphorus fertilizer into the bed at planting, and go off a soil test if you've got one. Then side-dress with a bit of nitrogen once the plants hit about 4 inches tall to keep them cruising along.
Pruning
Here's an easy one, kohlrabi needs no pruning at all. The only leaves you'll ever pull are the lower ones that go ragged from pests or disease, and those you just toss instead of leaving on the plant.
Size & spacing
These plants stay nice and small, only 6 to 12 inches (15 to 30 cm) tall and about as wide. Space the standard varieties roughly 4 inches (10 cm) apart so each one has room to fatten its bulb without getting crowded.
When to plant
Kohlrabi's a cool-weather crop, and it really doesn't like summer heat. Sow it in early spring for a late-spring harvest, then sow it again in July so the bulbs wrap up in the cool of fall. Both crops are done 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 goes wrong with kohlrabi comes down to timing and the usual cabbage-family pests it shares with its cousins. Catch them early and they're pretty easy to shut down. Just find what matches below, then jump in before the bulb or the leaves take any real damage.
Wilting plants that just won't grow
When a plant wilts and stops growing for no obvious reason, the answer's usually underground. Dig one up and check for the tunnels of cabbage maggots or the swollen, club-shaped lumps of clubroot. There's no saving one that's infected, so pull it and get rid of it, then move your brassicas to fresh ground on a four-year cycle and keep the soil pH up to keep clubroot down.
Fix:
- Remove and destroy affected plants
- Practice a 4-year rotation away from brassicas
Bulbs that came out tough and bitter
So the bulb's gone woody? It's almost always because it grew too big, so the trick is just to pick the next one sooner. Cut one open and if it's stringy inside, it either sat too long or got pushed around by heat and dry spells. Pick them at 2 to 3 inches (5 to 8 cm) across and keep the soil evenly damp, and they'll stay 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 chewed in the leaves
Those holes are the work of green caterpillars, and it's usually imported cabbageworms, cabbage loopers, or diamondback moth larvae. Flip a leaf and you'll catch them right there next to dark specks of frass. Just pick them off, add a little Bt if that's your thing, and slip a floating row cover over young plants so the moths can't get in to lay.
Fix:
- Handpick caterpillars
- Apply Bacillus thuringiensis (Bt) where appropriate
- Use floating row covers
Little pinholes all over young leaves
See those tiny holes? That's flea beetles, and they'll bounce off the second you get close. It looks rough on a seedling, but a healthy plant barely notices. Throw a row cover over the bed at planting and keep the plants well fed, and they'll grow right past it.
Fix:
- Use floating row covers at planting
- Maintain vigorous growth so plants outgrow damage
Toxicity
Good news, kohlrabi is completely safe, a food crop with nothing toxic in it for people or pets. The bulb and the leaves are both edible, so if a curious pet grabs a nibble, no big deal. The only thing to watch is how much, since any brassica can cause gas, and a big feed isn't great for horses.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Cats are totally fine around kohlrabi. A nibble of leaf or stem won't do a thing, though most cats couldn't care less about it anyway.
Dogs None
Dogs can have kohlrabi no problem, raw or plainly cooked. The only catch? A big helping might leave them a little gassy, and that's about it.
Horses Mild
A little bit won't bother a horse, but a big feed of any brassica can upset the gut or, given time, mess with the thyroid. Keep it to the odd treat and you're good.
Rabbits Safe
Rabbits are happy with both the leaves and the bulb. Just ease it in slowly and in small amounts so their gut can get used to a new green.
Livestock Safe
Cattle, goats, and sheep can graze kohlrabi just fine. Like with any brassica, work it in bit by bit instead of all at once.
Birds Safe
Backyard hens and other birds love pecking at the leaves and stem. There's nothing in the plant that'll hurt them.
People Safe
Kohlrabi is grown to be eaten, raw or cooked, and it's fine for people of any age. The crisp bulb and the leafy tops are both good eating.
As a brassica, large quantities can cause gas or mild goitrogenic effects; horses should not be fed large amounts.
Varieties
You'll only find a handful of kohlrabi varieties in most seed catalogs, mostly split up by color and size. Here are the ones actually worth knowing.
Purple Vienna
This one's an heirloom you'll spot by its deep purple skin over pale greenish-white flesh.
White Vienna
It's the everyday pale green kind, and folks love it for that crisp, mild flesh.
Kossak
Here's a giant storage type that stays tender even when it gets way bigger than regular kohlrabi.
How to propagate
Kohlrabi grows from seed, and that's it, and it's honestly about as easy as seed-starting ever gets.
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 comes up from seed easily, and honestly it doesn't ask for much. Start it indoors in early spring around 4 to 6 weeks before you transplant, or just sow it straight in the ground from mid-April through early May, then again in July for fall. Pop each seed in 1/4 to 1/2 inches (5 cm) deep and thin the standard plants to 4 inches (10 cm) apart. You'll see sprouts 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's the twist: the part you eat grows above the ground, not below it. That round globe is a swollen stem that puffs out from the base of the plant instead of digging down like a root would. And the old name German turnip? It's a bit of a red herring, because kohlrabi is really a brassica, way closer to cabbage than to any actual turnip.