Cold hardiness & minimum temperature

Is Old Man Saltbush (Atriplex nummularia)cold hardy? Hardiness zone & min temp

Also called Old man saltbush, Giant saltbush, Australian saltbush, Bluish saltbush.

More about old man saltbush

About Old Man Saltbush

Atriplex nummularia · also called Old man saltbush, Giant saltbush · edible

Atriplex nummularia is a large, fast-growing, evergreen shrub native to the arid and semi-arid interior of Australia, where it is one of the most ecologically and agriculturally significant native plants. Its silvery, salty leaves are used as a distinctive seasoning in modern Australian cuisine and provide highly nutritious browse for sheep and cattle in dryland farming. The single most important care fact is that this plant must have full sun and free-draining soil — it tolerates extreme salinity, alkalinity, and drought but is sensitive to waterlogging and high humidity. It is not listed as toxic by the ASPCA, but oxalate content means it should be classified as mildly-toxic for pets.

Cold limit: USDA 8-11 · RHS H3 (-5 to 45°C)

What old man saltbush's hardiness rating actually means

Old Man Saltbush is half-hardy (RHS H3). It survives a mild winter outdoors in a sheltered spot, but a hard frost kills it — so in colder zones it is lifted, potted, or grown as a tender plant. 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 8-11 — 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

Minimum survivable temperature is roughly about −5 to 1 °C — a light, short frost only. Old Man Saltbush shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for old man saltbush as it gets too cold:

Down to roughly about −5 to 1 °C it copes, especially if dry and sheltered.
A sustained hard frost collapses the top growth; whether it returns depends on whether the roots, crown or tubers froze.
Wet cold is far more lethal than dry cold for this plant — soggy, frozen soil is the usual killer.

Can old man saltbush go outside or overwinter — and where?

It can live outside year-round only in the mildest, most sheltered part of USDA 8-11 or a frost-free UK microclimate.
In colder zones, grow it in a pot you can move under cover, or lift its tubers/roots and store them frost-free over winter.
A south-facing wall, free-draining soil and a dry winter position can push it a full zone hardier than the books suggest.

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 old man saltbush 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 old man saltbush

Old Man Saltbush is right on a hardiness edge in many gardens, so if you are pushing it, these measures buy it the margin it needs:

Mulch the crown or root zone deeply with bark, straw or leaf-mould before the first hard frost.
Move container plants against a warm wall or into an unheated but frost-free porch or greenhouse.
Fleece the top growth on the coldest nights, and keep it on the dry side — dry roots survive cold far better than wet ones.
Lift dahlia-type tubers or tender crowns after the first light frost blackens the foliage and store them somewhere cool but frost-free.

Old Man Saltbush hardiness — frequently asked questions

Is old man saltbush cold hardy?

Old Man Saltbush is half-hardy (RHS H3). It survives a mild winter outdoors in a sheltered spot, but a hard frost kills it — so in colder zones it is lifted, potted, or grown as a tender plant. Borderline outdoors. In its mild end of USDA 8-11 (and sheltered UK gardens) old man saltbush can stay out; in colder areas it must be lifted, brought in, or treated as a frost-tender plant.

What is the minimum temperature old man saltbush can survive?

Minimum survivable temperature is roughly about −5 to 1 °C — a light, short frost only. Old Man Saltbush shrugs off cold nights but a real, sustained freeze will kill it.

What hardiness zone is old man saltbush?

Old Man Saltbush is rated USDA 8-11 and RHS H3 — Half-hardy — comes through mild UK winters outside but is killed by a hard freeze.

Can old man saltbush survive winter outside?

It can live outside year-round only in the mildest, most sheltered part of USDA 8-11 or a frost-free UK microclimate. In colder zones, grow it in a pot you can move under cover, or lift its tubers/roots and store them frost-free over winter. A south-facing wall, free-draining soil and a dry winter position can push it a full zone hardier than the books suggest.

How do I protect old man saltbush from frost?

Mulch the crown or root zone deeply with bark, straw or leaf-mould before the first hard frost. Move container plants against a warm wall or into an unheated but frost-free porch or greenhouse. Fleece the top growth on the coldest nights, and keep it on the dry side — dry roots survive cold far better than wet ones. Lift dahlia-type tubers or tender crowns after the first light frost blackens the foliage and store them somewhere cool but frost-free.