Cold hardiness & minimum temperature

Is Prickly Saltwort (Salsola kali)cold hardy? Hardiness zone & min temp

Also called Prickly saltwort, Prickly glasswort, Russian thistle (when a tumbleweed), Common saltwort.

More about prickly saltwort

About Prickly Saltwort

Salsola kali · also called Prickly saltwort, Prickly glasswort · edible

Salsola kali is a spiny, bushy annual in the amaranth family (Amaranthaceae) that colonises sandy beaches, strandlines, and coastal dunes from Europe's Atlantic and Baltic shores to Mediterranean coastlines, and is naturalised across North America as a common tumbleweed. It is highly salt-tolerant, drought-resistant, and adapted to nutrient-poor, well-drained sandy soils in full sun. Young shoots before the spines harden were historically eaten as a salted vegetable and the plant was once an important source of soda ash for glassmaking. Due to potential accumulation of oxalates and nitrates, it should be treated as mildly toxic to pets.

Cold limit: USDA 4-11 · RHS H6 (-15 to 40°C)

What prickly saltwort's hardiness rating actually means

Hardiness works differently for prickly saltwort: 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 4-11 — 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 prickly saltwort 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 prickly saltwort 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 prickly saltwort 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 prickly saltwort

Prickly Saltwort 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.

Prickly Saltwort hardiness — frequently asked questions

Is prickly saltwort cold hardy?

Hardiness works differently for prickly saltwort: 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. Prickly Saltwort is grown as an annual in USDA 4-11; you sow after the last frost and harvest before the first one, then start again next year.

What is the minimum temperature prickly saltwort 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 prickly saltwort?

Prickly Saltwort is rated USDA 4-11 and RHS H6 — Hardy throughout the UK and northern Europe.

Can prickly saltwort 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 prickly saltwort 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.