How to grow Kohlrabi in New Zealand
Kohlrabi is a quick, easy brassica grown for its swollen, round stem, which sits above the ground like a small turnip. It is crisp and mild, a bit like broccoli stem or swede, and good raw in salads and slaws or cooked. It is ready in about two months, and the secret is to pick it small, before it turns woody.
📖 Our full guide: How to Grow Kohlrabi in New Zealand
At a glance
When to sow by region
| Region | When to sow | Regional note |
|---|---|---|
| Northland | August to October, January to April | |
| Auckland | August to October, January to April | |
| Waikato & Bay of Plenty | August to October, January to April | |
| Central North Island | August to October, January to April | |
| Wellington & Lower North Island | August to October, January to April | |
| Nelson & Marlborough | August to October, January to April | |
| Canterbury | August to April | Keep sowing through Nov to Dec with steady watering. |
| Otago & Southland | September to March | Start spring sowings in Sep; the soil is too cold before then. Cool summers let you keep sowing through Nov to Dec. Make the last sowing in Mar so the crop is ready before winter growth stops. |
| Central Otago | September to March | Start spring sowings in Sep; the soil is too cold before then. Keep sowing through Nov to Dec with steady watering. Make the last sowing in Mar so the crop is ready before winter growth stops. |
Where to plant
Grow kohlrabi in full sun in firm, fertile, well-drained soil enriched with compost or blood and bone. It prefers cool growing conditions, and steady, even moisture keeps the stems tender; irregular watering makes them woody or split.
As a brassica, rotate it with the rest of the cabbage family, and avoid beds where brassicas grew recently.
- Northland, Auckland, Waikato and Bay of Plenty, the central North Island, Wellington, and Nelson and Marlborough: sow from August to October and from January to April.
- Canterbury: sow from August through to April, keeping summer sowings well watered.
- Otago and Southland and Central Otago: start spring sowings in September, as the soil is too cold before then, keep sowing through to December, and make the last sowing in March so the crop is ready before winter growth stops.
Choosing a variety
| Variety | Notes |
|---|---|
| Purple Vienna (Early Purple Vienna) | Purple skin and crisp white flesh, mild and sweet; slow to bolt |
| White Vienna | Pale green skin with the same crisp, mild flesh, quick to mature |
| Grand Duke F1 | A uniform hybrid |
Purple and green types taste the same inside.
How to plant
- Sow seed direct in clumps of two or three, about 6 mm to 1 cm deep, 15 to 20 cm apart in rows 30 to 40 cm apart. Seed germinates in about 7 to 14 days in soil of 10 to 20°C.
- Keep the soil moist, then thin each clump to the strongest seedling.
- Cover the bed with insect mesh to keep white butterfly off.
- Sow a new batch every four to five weeks for a steady supply.
Watering and feeding
Water regularly and evenly. Kohlrabi that dries out or gets a flood after a dry spell turns woody or splits.
Feed weekly with a liquid vegetable fertiliser for quick, tender growth.
Pruning and care through the year
- Do not mound soil around the swelling stem; it does not need support and mounding can make it rot.
- Keep the bed weeded, as slow, checked growth gives tough stems.
- Keep insect mesh on through the warmer months.
Harvesting
Pull or cut kohlrabi when the swollen stem is between golf ball and tennis ball size, about 5 to 8 cm across, usually eight to ten weeks after sowing. Smaller is tastier: large ones turn woody and fibrous.
Trim off the leaves and root. Kohlrabi keeps up to about two weeks in the fridge without its tops. Young leaves can be cooked like kale.
Growing in pots
Kohlrabi suits pots at least 30 cm wide and deep. Sow a few clumps, thin to the strongest, keep the mix evenly moist and feed weekly.
Companion planting
Kohlrabi is small and quick, so it slots between slower crops in a cool-season bed.
Good companions
- Beetroot Another quick crop for the same cool seasons that shares the bed easily.
- Onion Takes little space and grows alongside kohlrabi.
Keep apart
Avoid planting these close to kohlrabi.
- Tomato A summer crop with different needs; traditional lists keep it apart from brassicas.
- Strawberry Traditional companion lists keep strawberries apart from cabbage family crops.
Pests and diseases
Kohlrabi has the usual brassica pests. Insect mesh from sowing prevents most damage.
Pests to watch for
- White butterfly Green caterpillars and ragged holes in the leaves, mainly spring to autumn.
- Diamondback moth Small green caterpillars that wriggle when touched and leave windows in the leaves.
- Aphids Grey, waxy clusters under leaves.
Diseases to watch for
- Clubroot Plants wilt in warm weather and the roots are swollen and distorted. Rotate brassicas and lime acid soil.
Common questions
When is kohlrabi ready to pick?
When the swollen stem is between golf ball and tennis ball size, about 5 to 8 cm across, usually eight to ten weeks after sowing. Do not let it grow big, as it turns woody.
What does kohlrabi taste like?
Crisp and mild, like a sweet broccoli stem or a mild swede. Eat it raw in salads and slaws, or roast, steam or stir-fry it.
Why is my kohlrabi woody?
It was left too long, or growth was checked by dry soil or uneven watering. Pick small and water evenly.
When should I sow kohlrabi in New Zealand?
In most areas from August to October and from January to April. In Otago, Southland and Central Otago sow from September to December and again until March.
Is purple kohlrabi different from green?
Only on the outside. Purple and green types have the same crisp, white, mild flesh.
Sources we checked: Yates NZ: How to grow kohlrabi; Kings Seeds NZ: Kohlrabi Early Purple Vienna.