Cold hardiness & minimum temperature

Is Kai-lan (Gai Lan) (Brassica oleracea var. alboglabra)cold hardy? Hardiness zone & min temp

Also called kai-lan, gai lan, Chinese broccoli, Chinese kale.

More about kai-lan (gai lan)

About Kai-lan (Gai Lan)

Brassica oleracea var. alboglabra · also called kai-lan, gai lan · edible

Kai-lan, or Chinese broccoli, is a Brassica oleracea grown for thick, sweet flowering stems, blue-green leaves, and small white-budded heads. Harvested before full bloom in roughly 50-70 days, it has a robust broccoli-like flavour, tolerates heat better than heading broccoli, and resprouts side shoots after the main stem is cut.

Cold limit: USDA Grown as an annual in zones 2-11; more heat-tolerant than heading broccoli, frost-tender in flower · RHS H3 (tolerates light frost; not reliably hardy through hard freezes) (15-28°C)

What kai-lan (gai lan)'s hardiness rating actually means

Hardiness works differently for kai-lan (gai lan): 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 Grown as an annual in zones 2-11; more heat-tolerant than heading broccoli, frost-tender in flower — 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 kai-lan (gai lan) 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 kai-lan (gai lan) 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 kai-lan (gai lan) 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 kai-lan (gai lan)

Kai-lan (Gai Lan) 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.

Kai-lan (Gai Lan) hardiness — frequently asked questions

Is kai-lan (gai lan) cold hardy?

Hardiness works differently for kai-lan (gai lan): 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. Kai-lan (Gai Lan) is grown Grown as an annual in zones 2-11; more heat-tolerant than heading broccoli, frost-tender in flower; you sow after the last frost and harvest before the first one, then start again next year.

What is the minimum temperature kai-lan (gai lan) 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 kai-lan (gai lan)?

Kai-lan (Gai Lan) is rated USDA Grown as an annual in zones 2-11; more heat-tolerant than heading broccoli, frost-tender in flower and RHS H3 — Half-hardy — comes through mild UK winters outside but is killed by a hard freeze.

Can kai-lan (gai lan) 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 kai-lan (gai lan) 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.