Brassica
How to grow kohlrabi
Brassica oleracea (Gongylodes group)
Kohlrabi is a brassica grown for its swollen stem, which sits above the soil like a turnip on a stalk and is ready 8 to 12 weeks from sowing. Sow little and often from March to August in fertile, moist soil in full sun, direct or in modules, and space plants 15 to 20 cm apart. Grow it fast with steady water and pick at 5 to 7 cm across, before it turns woody.
- Hardiness
- Hardy
- Position
- Full sun
- Soil
- Fertile, moist, free-draining
- Ideal pH
- 6.5 to 7.5
- Water
- Moderate, keep steady for tender bulbs
- Feeding
- Moderate feeder
Sowing and planting kohlrabi
WhenSow Mar to Aug in succession; harvest 8 to 12 weeks later
Starting off
Direct or in modules every 3 weeks from March (fleeced) to August, germinating in 5 to 10 days at 10 to 20 °C; green types such as 'Quickstar' first, purple 'Azur Star' for later sowings and 'Superschmelz' in June for giant winter bulbs. Transplant at 4 weeks before the roots fill the cell.
Spacing and planting
Sow 1 to 2 cm deep in drills 30 cm apart and thin to 15 to 20 cm; module plants go out at the same spacing. Plant shallow, never deeper than the module, so the bulb sits above the soil. Good in a 20 cm deep trough with plants 15 cm apart.
Varieties worth growing
- Kolibri F1
- Purple skin, crisp white flesh and slow to go woody. The most widely grown purple variety, good for summer and autumn.
- Azur Star
- Early, blue-purple and slow to bolt, so it suits spring as well as late sowings.
- Olivia F1
- Pale green and uniform, with little fibre; a good choice for the earliest crops under fleece.
- Superschmelz
- Giant white kohlrabi that stays tender at 20 cm across or more. Sow in June for autumn and winter.
Kohlrabi month by month
Timings are for central England. Allow two weeks later in the north and on cold, heavy soil.
- January
Nothing to do.
- February
Order seed. Sow the first green varieties in modules under cover at the end of the month.
- March
Sow in modules or direct under fleece. Rake in the base dressing a week ahead.
- April
Plant out module plants at four weeks old, 15 to 20 cm apart. Sow again.
- May
First stems ready. Sow every three weeks. Keep mesh on against root fly and butterflies.
- June
Switch to purple varieties and sow Superschmelz for winter. Water in dry weather.
- July
Keep sowing. Mulch. Harvest at 5 to 7 cm.
- August
Last sowing in the first half of the month.
- September
Harvest. Check for caterpillars.
- October
Harvest late sowings. Net against pigeons.
- November
Cover the last plants with fleece or a cloche in hard frost and use them up.
- December
Pull the last of the late sowings. Otherwise nothing to do.
Feeding kohlrabi
A quick brassica that needs fertile soil from day one and nothing afterwards. One base dressing carries each sowing through to harvest.
A steady balanced feed, grow it fast for tender, swollen stems.
Feeding plan
The autumn or winter before
Garden compost
A 5 cm layer on the bed. Kohlrabi sits well after peas or beans, which leave the soil in good heart.
A week before sowing or planting
Fruit & Vegetable Fertiliser 4-5-6
100 g/m² raked into the surface. For rows 30 cm apart that is 30 g per metre of row.
Only on Superschmelz and other slow winter types, 6 weeks after planting
Fruit & Vegetable Fertiliser 4-5-6
50 g/m² between the plants, hoed in and watered, about 15 g per metre of row. That makes 150 g/m² for the season, the label maximum. Quick summer crops do not need it.
Signs to watch
Split or hollow bulbs with corky brown centres
Boron short, or dry soil followed by rain
Seaweed feed and steady water
Woody, fibrous bulbs
Left too long or a growth check, not nutrition
Pull at 6 cm and sow in succession
All leaf and a thin stem
Excess nitrogen
No feeding beyond the base dressing
Pests, diseases and problems
Young plants wilt and pull up easily, with the roots eaten away
Cabbage root fly maggots
Cover with fine insect mesh from sowing or planting, or fit a brassica collar round each transplant.
Ragged holes in the leaves, green caterpillars and droppings in the crown
Caterpillars of the large and small cabbage white butterflies, from May to October
Mesh keeps the butterflies off. Otherwise check the undersides of leaves twice a week and rub off the egg clusters and young caterpillars.
Seedling leaves pitted with small round holes
Flea beetle
Raise early plants in modules so they go out past the vulnerable stage, keep them watered, and use fleece or mesh on direct sowings.
Leaves torn to the ribs, especially on young plants and in winter
Wood pigeons
Net or mesh held on hoops above the plants.
Plants stunted and wilting in sun, roots thickened and distorted
Clubroot
Lime acid soil to pH 7 after a test, keep a four-year gap between brassicas, and raise plants in modules of clean compost to give them a head start.
Bulbs split open
Heavy rain or watering after a dry spell
Water regularly so growth never stops and starts, mulch in summer, and harvest on time.
Harvest and rotation
Harvest and storage
Pull when the swollen stem is 5 to 7 cm across, golf-ball to tennis-ball size, 8 to 12 weeks from sowing; only 'Superschmelz' stays tender larger. Cut the root off below the bulb and use the young leaves as greens. A 1 m row yields 6 to 8 bulbs. Keeps 2 weeks in the fridge with leaves removed; late sowings stand in the ground until December.
Rotation and companions
Rotation: brassica group, 4-year gap, though as a quick crop it fills gaps between slower brassicas. Beetroot and onions alongside share the bed without shading; lettuce between plants gives summer ground cover. Keep away from strawberries and tomatoes and from pole beans, which shade it.
Good to knowHarvest at golf-ball to tennis-ball size; older bulbs turn woody.
Growing kohlrabi in pots
Kohlrabi suits a trough or large pot at least 20 cm deep, with plants 15 cm apart: three in a 60 cm trough, or one to a 20 cm pot. Use multipurpose compost with the 4-5-6 mixed in at 5 g per litre, 100 g for a 20 litre trough, and no further feed. Set module plants no deeper than they were in the cell so the stem can swell above the surface. Water every day in summer; an irregular supply is what splits the bulbs. Quick varieties such as Olivia and Azur Star are the ones to choose.
Kohlrabi: common questions
When is kohlrabi ready to harvest?
Harvest when the swollen stem is 5 to 7 cm across, between golf-ball and tennis-ball size, which is 8 to 12 weeks from sowing. Cut the root off just below the bulb. Left longer, most varieties turn woody; Superschmelz is the exception.
Why is my kohlrabi not forming a bulb?
The usual causes are crowding, planting too deep, shade or a check to growth. Give each plant 15 to 20 cm, set transplants at the same depth as they were in the module, plant out before they are pot-bound and keep them watered. Excess nitrogen also gives leaf and a thin stem.
What does kohlrabi taste like and how do you eat it?
It tastes like a mild, sweet broccoli stalk with the crunch of an apple. Peel it and eat it raw in slices or grated into slaw, or steam, roast or stir-fry it. The young leaves can be cooked as greens.
Sources
Growing information on this page was checked against these references in November 2026. Feeding rates are Dr Forest label rates.