Cold hardiness & minimum temperature

Is Scarlet Runner Bean (Phaseolus coccineus)cold hardy? Hardiness zone & min temp

Also called Scarlet Runner Bean, Runner Bean, Multiflora Bean.

More about scarlet runner bean

About Scarlet Runner Bean

Phaseolus coccineus · also called Scarlet Runner Bean, Runner Bean · edible

A vigorous perennial vine grown as an annual in temperate climates, producing striking scarlet-red flowers beloved by hummingbirds and bees, and long flat pods up to 30 cm. Both the immature pods and mature shelled beans are edible. A dual-purpose ornamental and food plant; vines reach 3–4 m and need a strong trellis or tripod for support.

Cold limit: USDA 7–11 (tuberous roots perennial; grown as annual in zones 3–6) · RHS H2 (14–28 °C)

Watch for — Flower drop without pod set: The most common runner bean frustration. Caused by temperatures above 30 °C, drought at flowering, or lack of pollinators. Ensure consistent watering, plant early to avoid peak heat at flowering, and encourage bees with nearby pollinator-friendly plants.

What scarlet runner bean's hardiness rating actually means

Hardiness works differently for scarlet runner 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 H2 means: Tender — survives a frost-free greenhouse or a very mild, sheltered spot. On the US scale that maps to USDA 7–11 (tuberous roots perennial; grown as annual in zones 3–6) — 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 scarlet runner 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 scarlet runner 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 scarlet runner bean can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H2 figure above.

Frost protection for borderline scarlet runner bean

Scarlet Runner 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.

Scarlet Runner Bean hardiness — frequently asked questions

Is scarlet runner bean cold hardy?

Hardiness works differently for scarlet runner 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. Scarlet Runner Bean is grown 7–11 (tuberous roots perennial; grown as annual in zones 3–6); you sow after the last frost and harvest before the first one, then start again next year.

What is the minimum temperature scarlet runner 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 scarlet runner bean?

Scarlet Runner Bean is rated USDA 7–11 (tuberous roots perennial; grown as annual in zones 3–6) and RHS H2 — Tender — survives a frost-free greenhouse or a very mild, sheltered spot.

Can scarlet runner 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 scarlet runner 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.