Propagation guide

How to propagate Kohlrabi (Brassica oleracea var. gongylodes) — step by step

Also called German turnip, Turnip cabbage.

The best way to propagate kohlrabi

The reliable, beginner-friendly way to propagate kohlrabi is seed (with cuttings or suckering as a shortcut where possible). It suits this species because of how it grows: low, compact plant with a cluster of long-stalked leaves rising from a smooth, rounded stem that swells just above soil level into the edible 'bulb'.. From seed. Sow direct and thin, or sow in modules and transplant, from spring to late summer at 10-20°C, spacing plants 25-30 cm apart. Make small successional sowings every 3-4 weeks for a continuous supply.

For the wider picture of which technique suits which plant, our guide to plant propagation methods compares water, soil, leaf, division and offset propagation side by side.

Step-by-step: propagating kohlrabi

Start seed indoors. Sow kohlrabi seed into modules of fine compost 6–8 weeks before your last frost; keep at the right warmth until they germinate.
Grow on. Give bright light, pot on as roots fill the cell, and harden off over a week before they go outside.
Transplant out. Plant out only once the danger of frost has passed and the soil has warmed, at the spacing the crop needs.
Cutting shortcut. Where the plant suckers or roots from a softwood shoot, rooting a cutting clones a favourite specimen and skips the seedling stage.
Save your own seed. Let a strong, true-to-type plant set and ripen seed, then dry and store it cool and dark for next season.

The alternative method

If the main route does not suit your plant or setup, rooting a sucker / softwood cutting is the next best option for kohlrabi. Where the plant suckers or roots easily from a softwood shoot, a cutting clones a favourite specimen exactly and reaches a useful size faster than starting again from seed.

Timeline to roots

Realistically: seed to transplant in 4–8 weeks. These numbers assume spring or summer warmth and bright indirect light. In a cold, dark room — or in winter dormancy — the same kohlrabi propagation can take twice as long or stall completely, so do not panic if progress looks slow out of season. Patience beats poking: disturbing a forming root system to “check” on it is a common way to set it back.

Common failure points

Sowing or transplanting before the soil and air have genuinely warmed past the last frost.
Leggy seedlings from too little light indoors — they never fully recover.
Skipping hardening off, so transplants stall or scorch outdoors.
Saving seed from a hybrid and being surprised it does not come true.

When to do it

The best window is start indoors 6–8 weeks before last frost. Propagation is energetically expensive for a plant, and it only has the spare resources to build new roots when it is already growing actively, warm and well-lit. Out-of-season attempts are not pointless, but expect lower success and a longer wait.

Aftercare

Harden kohlrabi off over a week before planting out, water transplants in well, and protect them from late cold snaps. Steady moisture and the parent's light needs carry them through establishment. Match the parent's needs as the new kohlrabi settles: Full sun, at least 6 hours daily, for fast, even swelling of the stem. It tolerates light shade but bulbs up more slowly; weak light gives small, leafy plants with poor 'bulbs'.

Kohlrabi propagation — frequently asked questions

What is the best way to propagate kohlrabi?

Seed (with cuttings or suckering as a shortcut where possible) is the most reliable method for kohlrabi. Propagate kohlrabi mainly from seed — start it indoors 6–8 weeks before your last frost, or sow direct when soil warms. Where the plant suckers or roots from softwood, a cutting is a faster shortcut to a true-to-type clone of a favourite specimen.

Do you need a node to propagate kohlrabi?

For kohlrabi the rooting structure is seed (with cuttings or suckering as a shortcut where possible), so a classic "node" matters less than starting with the right plant material — Where the plant suckers or roots from softwood, a cutting is a faster shortcut to a true-to-type clone of a favourite specimen..

How long does it take kohlrabi to root?

Seed to transplant in 4–8 weeks. Timing varies with warmth and light — propagations move fastest in spring and summer when the plant is in active growth, and can stall almost completely in a cold, dark winter.

What is the best time of year to propagate kohlrabi?

Start indoors 6–8 weeks before last frost. Root and shoot development is metabolically demanding, so propagating during the active growing season gives noticeably higher success rates and faster results than attempting it in dormancy.

Can you propagate kohlrabi in water?

Where kohlrabi can be taken as a softwood cutting, that cutting can often be water-rooted; the main route, though, is seed sown into compost rather than water.