Cold hardiness & minimum temperature

Is Scorzonera (Scorzonera hispanica)cold hardy? Hardiness zone & min temp

Also called Black salsify, Spanish salsify.

More about scorzonera

About Scorzonera

Scorzonera hispanica · also called Black salsify, Spanish salsify · edible

Scorzonera is a hardy perennial grown as an annual or biennial for its long, black-skinned, white-fleshed taproot. Slow to establish, it needs deep, stone-free soil and a long season, but roots can stay in the ground over winter and even thicken in a second year. The flesh has a mild, slightly sweet flavour.

Cold limit: USDA 3-9 (perennial; roots overwinter and can be lifted as needed) · RHS H6 (hardy through most UK winters; roots survive in the ground) (15-21°C)

Watch for — Bolting in the first year: Cold stress after sowing can push the perennial into early flowering, making roots tough and pithy. Sow into warmed soil and avoid prolonged cold checks.

What scorzonera's hardiness rating actually means

Hardiness works differently for scorzonera: 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 H6 means: Hardy throughout the UK and northern Europe. On the US scale that maps to USDA 3-9 (perennial; roots overwinter and can be lifted as needed) — 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 scorzonera 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 scorzonera 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 scorzonera can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H6 figure above.

Frost protection for borderline scorzonera

Scorzonera 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.

Scorzonera hardiness — frequently asked questions

Is scorzonera cold hardy?

Hardiness works differently for scorzonera: 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. Scorzonera is grown as an annual in USDA 3-9 (perennial; roots overwinter and can be lifted as needed); you sow after the last frost and harvest before the first one, then start again next year.

What is the minimum temperature scorzonera 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 scorzonera?

Scorzonera is rated USDA 3-9 (perennial; roots overwinter and can be lifted as needed) and RHS H6 — Hardy throughout the UK and northern Europe.

Can scorzonera 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 scorzonera 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.