Cold hardiness & minimum temperature

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

Also called Monarch celeriac, celery root.

More about celeriac 'monarch'

About Celeriac 'Monarch'

Apium graveolens var. rapaceum 'Monarch' · also called Monarch celeriac, celery root · edible

'Monarch' is an award-winning celeriac prized for large, smooth, rounded crowns with few side roots and sweet, nutty white flesh that stays pale when cut. A long-season crop of 100-120 days, it is sown indoors in early spring, planted out after frost, and lifted in autumn. Constant moisture and rich, fertile soil are essential for full-sized, clean crowns.

Cold limit: USDA 8-10 (grown as a long-season annual; exposed crowns damaged below about -3°C) · RHS H3 (15-21°C)

Watch for — Bolting: A cold check after planting out or a drought spell makes plants flower prematurely and ruins the crown. Plant only after frost has passed and keep moisture even throughout.

What celeriac 'monarch''s hardiness rating actually means

Hardiness works differently for celeriac 'monarch': 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 H3 means: Half-hardy — comes through mild UK winters outside but is killed by a hard freeze. On the US scale that maps to USDA 8-10 (grown as a long-season annual; exposed crowns damaged below about -3°C) — 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 'monarch' 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 'monarch' 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 'monarch' can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H3 figure above.

Frost protection for borderline celeriac 'monarch'

Celeriac 'Monarch' 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 'Monarch' hardiness — frequently asked questions

Is celeriac 'monarch' cold hardy?

Hardiness works differently for celeriac 'monarch': 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 'Monarch' is grown 8-10 (grown as a long-season annual; exposed crowns damaged below about -3°C); you sow after the last frost and harvest before the first one, then start again next year.

What is the minimum temperature celeriac 'monarch' 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 'monarch'?

Celeriac 'Monarch' is rated USDA 8-10 (grown as a long-season annual; exposed crowns damaged below about -3°C) and RHS H3 — Half-hardy — comes through mild UK winters outside but is killed by a hard freeze.

Can celeriac 'monarch' 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 'monarch' 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.