Cold hardiness & minimum temperature

Is Cobaea scandens (Cobaea scandens)cold hardy? Hardiness zone & min temp

Also called cup and saucer vine, cathedral bells, Mexican ivy.

More about cobaea scandens

About Cobaea scandens

Cobaea scandens · also called cup and saucer vine, cathedral bells · flowering

Cobaea scandens, the cup and saucer vine, is a fast, tender perennial climber usually grown as an annual for its large bell-shaped flowers that open creamy-green and age to deep purple, each set in a leafy green ruff. It climbs rapidly by branched tendrils, flowers from summer to first frost, and quickly covers trellis, arches or fences in a single season.

Cold limit: USDA 9-11 (grown as an annual in cooler zones) · RHS H2 (5 to 28°C)

Watch for — Frost kills the plant: It is tender and dies at the first frost. Sow under glass in spring, plant out only after frosts, and treat it as an annual in cool climates.

What cobaea scandens's hardiness rating actually means

Hardiness works differently for cobaea scandens: 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 9-11 (grown as an annual in cooler zones) — 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 cobaea scandens 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 cobaea scandens 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 cobaea scandens 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 cobaea scandens

Cobaea scandens 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.

Cobaea scandens hardiness — frequently asked questions

Is cobaea scandens cold hardy?

Hardiness works differently for cobaea scandens: 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. Cobaea scandens is grown 9-11 (grown as an annual in cooler zones); you sow after the last frost and harvest before the first one, then start again next year.

What is the minimum temperature cobaea scandens 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 cobaea scandens?

Cobaea scandens is rated USDA 9-11 (grown as an annual in cooler zones) and RHS H2 — Tender — survives a frost-free greenhouse or a very mild, sheltered spot.

Can cobaea scandens 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 cobaea scandens 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.