Cold hardiness & minimum temperature

Is Pak Choi (Brassica rapa subsp. chinensis)cold hardy? Hardiness zone & min temp

Also called Bok choy, Chinese cabbage, Pak choy.

More about pak choi

About Pak Choi

Brassica rapa subsp. chinensis · also called Bok choy, Chinese cabbage · edible

Pak choi is a fast, succulent Asian brassica grown for its crisp white or green leaf stalks and tender dark leaves in a loose, non-heading rosette. It crops in as little as 4-8 weeks and is ideal for stir-fries. Quick and easy, it suits spring and late-summer sowings; hot, dry conditions and long days readily trigger bolting, so cool, moist growing is key.

Cold limit: USDA 2-11 (grown as a cool-season annual; tolerates light frost) · RHS H3 (13-21°C)

What pak choi's hardiness rating actually means

Hardiness works differently for pak choi: 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 H3 means: Half-hardy — comes through mild UK winters outside but is killed by a hard freeze. On the US scale that maps to USDA 2-11 (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 pak choi 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 pak choi 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 pak choi can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H3 figure above.

Frost protection for borderline pak choi

Pak Choi 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.

Pak Choi hardiness — frequently asked questions

Is pak choi cold hardy?

Hardiness works differently for pak choi: 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. Pak Choi is grown 2-11 (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 pak choi 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 pak choi?

Pak Choi is rated USDA 2-11 (grown as a cool-season annual; tolerates light frost) and RHS H3 — Half-hardy — comes through mild UK winters outside but is killed by a hard freeze.

Can pak choi 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 pak choi 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.