Kohlrabi
Brassica oleracea var. gongylodes
Kohlrabi is an underrated brassica that produces a swollen, turnip-like stem above ground in just 8–10 weeks. The crisp, mild flesh tastes like a sweet cross between cabbage stalk and apple — delicious raw in salads or roasted. Sow successionally from March to August for a long season. Spring sowings can be started in modules under cover; later sowings go direct. Harvest when bulbs reach 7–10cm across — leave longer and they turn woody. Green varieties like 'Korridor F1' are fastest; purple 'Kolibri F1' looks striking and stores slightly longer. Cover with fine mesh to exclude cabbage root fly and butterflies. Bolt-resistant modern varieties are essential for summer sowings.
Plan where to grow Kohlrabi using our vegetable garden planner.
When to Sow Kohlrabi
Sow kohlrabi in March, April, May, June, July, August.
Time to Harvest Kohlrabi
Expect to harvest approximately 2 months after sowing, usually from May to November.
Companion Plants for Kohlrabi
- Butterhead Lettuce
Both are quick, compact crops that can share a bed and be harvested young.
- Red Onion
Onions are traditionally grown near brassicas in the belief their scent helps mask them from pests.
- Beetroot
Beetroot and kohlrabi are a traditional pairing; both are compact, quick and harvested at a similar size.
- Dill
Dill flowers attract hoverflies and parasitic wasps that prey on aphids and caterpillars.
- Spring Onion
Spring onions fit between kohlrabi plants and their scent may help confuse brassica pests.
- Lamb's Lettuce
Lamb's lettuce makes useful ground cover around kohlrabi in late summer and autumn.
Expected Yield
A 1m row yields 10–12 bulbs, around 1.5–2kg total.
Common Problems with Kohlrabi
Woody, tough bulbs
Caused by harvesting too late or inconsistent watering. Pick at tennis-ball size (7–10cm). Water generously and consistently — drought followed by rain causes splitting and woodiness.
Cabbage root fly
Larvae burrow into roots, causing wilting. Fit brassica collars around stems at transplanting, or cover the bed with fine mesh from sowing.
Bolting before bulbing
Heat and water stress cause flowering before the stem swells. Choose bolt-resistant F1 varieties for summer sowings and water regularly during hot spells.
Kohlrabi: common questions
When should I sow kohlrabi in the UK?
Sow kohlrabi from March to August. Sow under cover for an early start, or directly outside once the soil has warmed.
How far apart should I plant kohlrabi?
Space kohlrabi about 25cm apart. It grows to around 40cm tall. Sow seeds 1cm deep.
How long does kohlrabi take to germinate?
Kohlrabi seeds usually germinate in 5–10 days, depending on temperature.
When is kohlrabi ready to harvest?
In the UK, kohlrabi is usually harvested from May to November. It's ready about 2 months after sowing.
Does kohlrabi come back every year?
No. Kohlrabi is a biennial that's grown for a single season: it's harvested in its first year, before it would flower, so sow it fresh each year.
What grows well with kohlrabi?
Good companions for kohlrabi include Butterhead Lettuce, Red Onion, Beetroot, Dill and Spring Onion. See the companion plants section above for why each one helps.
Is kohlrabi frost hardy?
Yes. Kohlrabi is hardy and survives a normal UK winter outdoors.
Is kohlrabi a brassica?
Yes. Kohlrabi belongs in the brassicas group for crop rotation. Grow it in a different bed each year, alongside other brassicas, so pests and diseases don't build up in the soil.
Plan your kohlrabi in the allotment planner
Drag and drop plants onto your plot and get personalised sowing reminders.
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