Mature size & growth rate

How big does Kohlrabi (Brassica oleracea var. gongylodes) get?

Also called German turnip, Turnip cabbage.

More about kohlrabi

About Kohlrabi

Brassica oleracea var. gongylodes · also called German turnip, Turnip cabbage · edible

Kohlrabi is a fast, easy brassica grown for its swollen, globe-shaped stem that sits above ground, with a crisp, mild, turnip-meets-cabbage flavour. Green and purple types crop in 8-10 weeks. Sow successionally from spring, keep it growing steadily in fertile, moist soil and full sun, and harvest while the bulbs are young and tender, before they turn woody.

Mature size: 25-30 cm tall and wide, with bulbs best harvested at 5-8 cm across

Watch for — Woody, split bulbs: Caused by drought, irregular watering or leaving bulbs too long. Keep moisture even and harvest young, ideally when the swollen stem is tennis-ball sized or smaller.

Indoor size vs how big it gets in the wild

Kohlrabi reaches its full size within one growing season — there is no "long-term" size, just how big it gets before you harvest or it dies back. Indoors and in a pot, expect 25-30 cm tall and wide, with bulbs best harvested at 5-8 cm across. A pot, your light levels and a little pruning are what set the final size in a home, far more than the plant's theoretical potential.

It sizes up fast and once, racing from seedling to full size in a single season; after cropping it is finished, so size is a within-season question.

Growth rate and years to mature

Kohlrabi is a fast grower. Realistically, expect a single growing season — it reaches full size in one year, then is done. Its feeding profile backs this up: moderate feeder. work a balanced general fertiliser into the bed before sowing. on poorer soils, a single nitrogen side-dressing as plants establish keeps growth steady; avoid excess nitrogen, which delays bulbing and grows leaves at the expense of the stem.

Want this turned into the right next pot at the right moment? The pot size calculator and the kohlrabi repotting guide cover when and how much to size up — pot size is one of the biggest levers on how fast kohlrabi grows.

How to keep kohlrabi smaller

You are not stuck with the maximum size. For kohlrabi specifically, these are the levers, in order of impact:

Choose a compact or dwarf variety of kohlrabi from the start — that is the most reliable size control for an annual.
Grow it in a smaller container to naturally limit how large it gets.
For some crops, pinching or pruning the growing tips keeps the plant shorter and bushier.
Sow a little later or space plants closer if you specifically want smaller individual plants.

How to grow kohlrabi bigger or faster

If you want it to fill the space sooner, push the conditions rather than hoping — for kohlrabi the accelerators are:

Full sun, warm soil and steady water are what drive a crop to full size fastest.
Sow at the right time for your zone so it gets the whole season to size up.
Feed appropriately for the crop and never let it check (stall) from drought or cold.

Light is almost always the ceiling. The kohlrabi light requirements page covers exactly how bright a spot it needs to grow at its potential instead of stalling.

When kohlrabi outgrows the room (or the pot)

"Too big" usually arrives as one of these signs for kohlrabi:

It sprawls beyond its bed or container before harvest — usually a spacing or support issue.
It flops or needs staking once it hits full height.
Once it has fruited or bolted, it is at its final size for good — the next plant is a new sowing.

If it is the pot rather than the room, it is a repotting job, not a goodbye — see the kohlrabi repotting guide. If you want more of this plant instead of a bigger one, the kohlrabi propagation guide turns prunings into new plants.

Kohlrabi size — frequently asked questions

How big does kohlrabi get?

Kohlrabi reaches 25-30 cm tall and wide, with bulbs best harvested at 5-8 cm across when grown indoors. It sizes up fast and once, racing from seedling to full size in a single season; after cropping it is finished, so size is a within-season question.

Is kohlrabi slow or fast growing?

Kohlrabi is a fast grower. Expect a single growing season — it reaches full size in one year, then is done. Kohlrabi reaches its full size within one growing season — there is no "long-term" size, just how big it gets before you harvest or it dies back.

How long does kohlrabi take to reach full size?

Roughly a single growing season — it reaches full size in one year, then is done. Light, pot size and feeding move that timeline more than anything else.

How do I keep kohlrabi smaller?

Choose a compact or dwarf variety of kohlrabi from the start — that is the most reliable size control for an annual. Grow it in a smaller container to naturally limit how large it gets. For some crops, pinching or pruning the growing tips keeps the plant shorter and bushier. Sow a little later or space plants closer if you specifically want smaller individual plants.

How can I make kohlrabi grow bigger or faster?

Full sun, warm soil and steady water are what drive a crop to full size fastest. Sow at the right time for your zone so it gets the whole season to size up. Feed appropriately for the crop and never let it check (stall) from drought or cold.