Cold hardiness & minimum temperature

Is Kohlrabi (Brassica oleracea var. gongylodes)cold hardy? Hardiness zone & min temp

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.

Cold limit: USDA 3-11 (grown as a cool-season annual; tolerates light frost) · RHS H4 (15-24°C)

Watch for — Bolting: Cold checks to young plants or hot, dry spells can trigger premature flowering before the bulb forms. Sow into warm conditions and keep growth steady and unstressed.

What kohlrabi's hardiness rating actually means

Hardiness works differently for kohlrabi: it is grown as a seasonal crop, not overwintered. The question is not "what zone" but "how long is your frost-free growing window". Its RHS rating of H4 means: Hardy in an average winter across much of the temperate world. On the US scale that maps to USDA 3-11 (grown as a cool-season annual; tolerates light frost) — the zones where it can be left outdoors year-round.

New to these scales? The USDA hardiness zone map explained covers how the zone numbers work, and you can find your own zone with the zone finder.

Minimum temperature — and what happens below it

As an annual crop, its "minimum temperature" is the first hard frost — that is the end of the plant's life, not a survivable low. Many types are also damaged by light frost (around 0 °C).

Concretely, for kohlrabi as it gets too cold:

Light frost (around 0 to −2 °C) damages or kills tender summer crops outright; cold-hardy types take a few degrees of frost.
The plant does not "survive winter" — its life cycle simply ends, by design, when frost arrives or it finishes cropping.
A surprise late spring frost can also kill young transplants set out too early, before the season even starts.

Can kohlrabi go outside or overwinter — and where?

Time it to your frost dates: sow or plant out after the last spring frost, and aim to harvest before the first autumn frost.
In short-season zones, start it indoors or under cover to stretch the effective growing window.
Hardier crops in this group can be sown for an autumn or overwintered harvest in mild zones — check the specific crop.

Work back from your local frost dates with the frost-date calculator: the last spring frost and first autumn frost are what really decide when kohlrabi can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H4 figure above.

Frost protection for borderline kohlrabi

Kohlrabi is right on a hardiness edge in many gardens, so if you are pushing it, these measures buy it the margin it needs:

Use fleece, cloches or a cold frame at each end of the season to dodge a borderline frost and add growing weeks.
Have row cover ready for an unexpected late spring or early autumn frost.
Know your local last- and first-frost dates and count back the crop’s days-to-maturity to schedule the sowing.

Kohlrabi hardiness — frequently asked questions

Is kohlrabi cold hardy?

Hardiness works differently for kohlrabi: it is grown as a seasonal crop, not overwintered. The question is not "what zone" but "how long is your frost-free growing window". A seasonal crop, not a perennial. Kohlrabi is grown 3-11 (grown as a cool-season annual; tolerates light frost); you sow after the last frost and harvest before the first one, then start again next year.

What is the minimum temperature kohlrabi can survive?

As an annual crop, its "minimum temperature" is the first hard frost — that is the end of the plant's life, not a survivable low. Many types are also damaged by light frost (around 0 °C).

What hardiness zone is kohlrabi?

Kohlrabi is rated USDA 3-11 (grown as a cool-season annual; tolerates light frost) and RHS H4 — Hardy in an average winter across much of the temperate world.

Can kohlrabi survive winter outside?

Time it to your frost dates: sow or plant out after the last spring frost, and aim to harvest before the first autumn frost. In short-season zones, start it indoors or under cover to stretch the effective growing window. Hardier crops in this group can be sown for an autumn or overwintered harvest in mild zones — check the specific crop.

How do I protect kohlrabi from frost?

Use fleece, cloches or a cold frame at each end of the season to dodge a borderline frost and add growing weeks. Have row cover ready for an unexpected late spring or early autumn frost. Know your local last- and first-frost dates and count back the crop’s days-to-maturity to schedule the sowing.