Cold hardiness & minimum temperature

Is Winter Tarragon (Tagetes filifolia)cold hardy? Hardiness zone & min temp

Also called Irish Lace Marigold, Filigree Marigold.

More about winter tarragon

About Winter Tarragon

Tagetes filifolia · also called Irish Lace Marigold, Filigree Marigold · herb

Tagetes filifolia, sold as winter tarragon or Irish lace, is a tender marigold relative from Mexico and Central America. It forms a mound of finely divided, thread-like bright green foliage that smells of anise and licorice, used as a tarragon substitute. Tiny pale flowers appear in autumn. It needs warmth and full sun to thrive.

Cold limit: USDA 9-11 (grown as an annual in cooler zones) · RHS H2 (15-28°C)

Watch for — Root rot in wet soil: Cold, soggy soil rots the roots. Use a free-draining mix and let the surface dry before watering again.

What winter tarragon's hardiness rating actually means

Hardiness works differently for winter tarragon: 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 9-11 (grown as an annual in cooler zones) — 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 winter tarragon 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 winter tarragon 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 winter tarragon 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 winter tarragon

Winter Tarragon 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.

Winter Tarragon hardiness — frequently asked questions

Is winter tarragon cold hardy?

Hardiness works differently for winter tarragon: 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. Winter Tarragon is grown 9-11 (grown as an annual in cooler zones); you sow after the last frost and harvest before the first one, then start again next year.

What is the minimum temperature winter tarragon 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 winter tarragon?

Winter Tarragon is rated USDA 9-11 (grown as an annual in cooler zones) and RHS H2 — Tender — survives a frost-free greenhouse or a very mild, sheltered spot.

Can winter tarragon 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 winter tarragon 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.