Cold hardiness & minimum temperature

Is Black Turtle Bean (Phaseolus vulgaris 'Black Turtle')cold hardy? Hardiness zone & min temp

Also called Black Turtle Bean, Black Bean, Frijol Negro.

More about black turtle bean

About Black Turtle Bean

Phaseolus vulgaris 'Black Turtle' · also called Black Turtle Bean, Black Bean · edible

A compact bush bean grown primarily for its glossy, jet-black dried seeds, a staple of Latin American, Caribbean, and Southwestern US cuisine. Plants mature in 85–100 days and thrive in warm, sunny conditions. Allow pods to dry fully on the vine before harvesting. Excellent protein source; stores dried for years.

Cold limit: USDA 3–11 (frost-tender annual) · RHS H1c (18–32 °C)

What black turtle bean's hardiness rating actually means

Hardiness works differently for black turtle 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 3–11 (frost-tender annual) — 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 black turtle 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 black turtle 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 black turtle 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 black turtle bean

Black Turtle 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.

Black Turtle Bean hardiness — frequently asked questions

Is black turtle bean cold hardy?

Hardiness works differently for black turtle 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. Black Turtle Bean is grown 3–11 (frost-tender annual); you sow after the last frost and harvest before the first one, then start again next year.

What is the minimum temperature black turtle 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 black turtle bean?

Black Turtle Bean is rated USDA 3–11 (frost-tender annual) and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can black turtle 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 black turtle 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.