Cold hardiness & minimum temperature

Is Yardlong Bean (Vigna unguiculata subsp. sesquipedalis)cold hardy? Hardiness zone & min temp

Also called Asparagus bean, Snake bean, Chinese long bean.

More about yardlong bean

About Yardlong Bean

Vigna unguiculata subsp. sesquipedalis · also called Asparagus bean, Snake bean · edible

Yardlong bean (Vigna unguiculata subsp. sesquipedalis) is a heat-loving climbing relative of the cowpea grown for its remarkably long, slender pods that can reach 40-90 cm. A tropical annual, it thrives in hot summers, twining vigorously up tall supports. Pick pods young and tender for stir-fries; it tolerates heat far better than common green beans.

Cold limit: USDA Grown as a warm-season annual; best in zones 8-11, needs long hot summers (frost-tender) · RHS H1c (20-32°C)

What yardlong bean's hardiness rating actually means

Hardiness works differently for yardlong bean: 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 H1c means: Warm-temperate — can summer outdoors but must come in well before the first frost. On the US scale that maps to USDA Grown as a warm-season annual; best in zones 8-11, needs long hot summers (frost-tender) — 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 yardlong bean 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 yardlong bean 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 yardlong bean can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1c figure above.

Frost protection for borderline yardlong bean

Yardlong Bean 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.

Yardlong Bean hardiness — frequently asked questions

Is yardlong bean cold hardy?

Hardiness works differently for yardlong bean: 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. Yardlong Bean is grown Grown as a warm-season annual; best in zones 8-11, needs long hot summers (frost-tender); you sow after the last frost and harvest before the first one, then start again next year.

What is the minimum temperature yardlong bean 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 yardlong bean?

Yardlong Bean is rated USDA Grown as a warm-season annual; best in zones 8-11, needs long hot summers (frost-tender) and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can yardlong bean 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 yardlong bean 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.