Cold hardiness & minimum temperature

Is Radicchio 'Rossa di Treviso' (Cichorium intybus var. foliosum 'Rossa di Treviso')cold hardy? Hardiness zone & min temp

Also called Treviso radicchio, Italian chicory, Treviso red chicory.

More about radicchio 'rossa di treviso'

About Radicchio 'Rossa di Treviso'

Cichorium intybus var. foliosum 'Rossa di Treviso' · also called Treviso radicchio, Italian chicory · edible

'Rossa di Treviso' is an elongated Italian chicory forming upright, loose heads of wine-red leaves with bright white midribs. Cool weather and autumn frost intensify the colour and sweeten the pleasantly bitter leaves. A traditional cut-and-force crop, it is sown in summer for autumn and winter harvest in cooler climates.

Cold limit: USDA Grown as a cool-season annual/biennial; tolerates light frost · RHS H4 (10 to 20°C)

Watch for — Weak red colour: Colour develops with cooling autumn temperatures and light frost. Heads grown only in warm weather stay green and bitter; time the crop for cooling weather to redden the leaves.

What radicchio 'rossa di treviso''s hardiness rating actually means

Hardiness works differently for radicchio 'rossa di treviso': 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 a cool-season annual/biennial; tolerates 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 radicchio 'rossa di treviso' 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 radicchio 'rossa di treviso' 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 radicchio 'rossa di treviso' 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 radicchio 'rossa di treviso'

Radicchio 'Rossa di Treviso' 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.

Radicchio 'Rossa di Treviso' hardiness — frequently asked questions

Is radicchio 'rossa di treviso' cold hardy?

Hardiness works differently for radicchio 'rossa di treviso': 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. Radicchio 'Rossa di Treviso' is grown Grown as a cool-season annual/biennial; tolerates light frost; you sow after the last frost and harvest before the first one, then start again next year.

What is the minimum temperature radicchio 'rossa di treviso' 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 radicchio 'rossa di treviso'?

Radicchio 'Rossa di Treviso' is rated USDA Grown as a cool-season annual/biennial; tolerates light frost and RHS H4 — Hardy in an average winter across much of the temperate world.

Can radicchio 'rossa di treviso' 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 radicchio 'rossa di treviso' 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.