Cold hardiness & minimum temperature

Is Celeriac (Apium graveolens var. rapaceum)cold hardy? Hardiness zone & min temp

Also called Celery root, Knob celery, Turnip-rooted celery.

More about celeriac

About Celeriac

Apium graveolens var. rapaceum · also called Celery root, Knob celery · edible

Celeriac is a long-season biennial grown as an annual for its swollen, knobbly hypocotyl. It demands constant moisture, rich soil, and a 100-120 day stretch of cool weather. Start seed indoors 8-10 weeks before last frost, transplant after frost, and harvest before hard freezes. The flavour is celery-like but earthier and sweeter.

Cold limit: USDA Grown as an annual; seedlings hardy to about -2°C, mature roots tolerate light frost · RHS H4 (hardy through most of the UK as an overwintering root) (15-21°C)

Watch for — Premature bolting: A cold spell below 10°C for an extended period after transplanting vernalises the biennial and triggers flowering. Don't set out plants too early, and use bolt-resistant cultivars.

What celeriac's hardiness rating actually means

Hardiness works differently for celeriac: 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 H4 means: Hardy in an average winter across much of the temperate world. On the US scale that maps to USDA Grown as an annual; seedlings hardy to about -2°C, mature roots tolerate light 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 celeriac 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 celeriac 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 celeriac can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H4 figure above.

Frost protection for borderline celeriac

Celeriac 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.

Celeriac hardiness — frequently asked questions

Is celeriac cold hardy?

Hardiness works differently for celeriac: 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. Celeriac is grown Grown as an annual; seedlings hardy to about -2°C, mature roots tolerate light frost; you sow after the last frost and harvest before the first one, then start again next year.

What is the minimum temperature celeriac 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 celeriac?

Celeriac is rated USDA Grown as an annual; seedlings hardy to about -2°C, mature roots tolerate light frost and RHS H4 — Hardy in an average winter across much of the temperate world.

Can celeriac 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 celeriac 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.