Cold hardiness & minimum temperature

Is Courgette (Cucurbita pepo 'Defender')cold hardy? Hardiness zone & min temp

Also called courgette, zucchini, summer squash.

More about courgette

About Courgette

Cucurbita pepo 'Defender' · also called courgette, zucchini · edible

Courgette, or zucchini, is a fast, prolific bush summer squash cropping heavily from midsummer to first frost. It is a hungry, thirsty, tender annual needing full sun, very rich moist soil and warmth. Keep picking fruits young to sustain production; a couple of healthy plants can overwhelm a household with fruit through the season.

Cold limit: USDA Tender annual; grown in zones 3-11 after the last frost · RHS H2 (18-27°C)

Watch for — Poor fruit set and rotting tips: Young fruit shrivels and rots at the tip when cold, wet weather or lack of pollinators prevents pollination. Encourage pollinators, hand-pollinate if needed, and pick fruit young to keep plants productive.

What courgette's hardiness rating actually means

Hardiness works differently for courgette: 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 Tender annual; grown in zones 3-11 after the last frost — 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 courgette 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 courgette 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 courgette 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 courgette

Courgette 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.

Courgette hardiness — frequently asked questions

Is courgette cold hardy?

Hardiness works differently for courgette: 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. Courgette is grown Tender annual; grown in zones 3-11 after the last frost; you sow after the last frost and harvest before the first one, then start again next year.

What is the minimum temperature courgette 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 courgette?

Courgette is rated USDA Tender annual; grown in zones 3-11 after the last frost and RHS H2 — Tender — survives a frost-free greenhouse or a very mild, sheltered spot.

Can courgette 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 courgette 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.