Cold hardiness & minimum temperature

Is Asparagus fern (Asparagus aethiopicus)cold hardy? Hardiness zone & min temp

Also called foxtail fern (Sprengeri), lace fern.

About Asparagus fern

Asparagus aethiopicus · also called foxtail fern (Sprengeri), lace fern · houseplant

Asparagus fern is not a true fern but a relative of edible asparagus, with feathery emerald foliage on arching stems. Hardy and forgiving but mildly toxic to pets and possessed of small thorns that scratch skin. Drops needles when stressed.

Asparagus aethiopicus from southern Africa; despite the name it is not a true fern but a member of the asparagus family, with feathery cladodes rather than true leaves and a fleshy water-storing tuberous root system.

Arching plumed stems with sharp spines; ASPCA lists it as toxic to cats and dogs, the red berries containing sapogenin steroids causing GI upset, and repeated skin contact can cause dermatitis.

Cold limit: USDA 9-11 (indoor in most US homes) · RHS H1c (15-24°C)

Sources: aspca.org, en.wikipedia.org

What asparagus fern's hardiness rating actually means

Asparagus fern is not cold hardy. It is a tropical houseplant that dies if it is left out through frost — there is no zone where it overwinters outdoors in a UK or cold-US climate. Its RHS rating of H1c means: Warm-temperate — can summer outdoors but must come in well before the first frost. On the US scale that maps to USDA 9-11 (indoor in most US homes) — 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 °C (and never frost). Asparagus fern has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for asparagus fern as it gets too cold:

Below about about 5 °C, growth stalls and the leaves start to show cold stress — dark, water-soaked, or yellowing patches.
A single light frost blackens the foliage; a hard freeze kills the whole plant, roots included, and it does not recover.
Even a cold, draughty windowsill or an unheated porch in winter can be enough to damage it permanently.

Can asparagus fern go outside or overwinter — and where?

It can holiday outdoors in summer once nights are reliably above 5 °C, in shade or dappled light, hardened off gradually.
Bring it back indoors well before the first autumn frost — do not wait for a frost warning, move it when nights drop toward 10-12 °C.
It will never overwinter outside in a temperate climate; the indoors is its winter home, full stop.

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 asparagus fern can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1c figure above.

Asparagus fern hardiness — frequently asked questions

Is asparagus fern cold hardy?

Asparagus fern is not cold hardy. It is a tropical houseplant that dies if it is left out through frost — there is no zone where it overwinters outdoors in a UK or cold-US climate. Indoor-only in almost every home. Asparagus fern can only live outside year-round in genuinely frost-free climates (roughly USDA 9-11 (indoor in most US homes)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature asparagus fern can survive?

Minimum survivable temperature is roughly about 5 °C (and never frost). Asparagus fern has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

What hardiness zone is asparagus fern?

Asparagus fern is rated USDA 9-11 (indoor in most US homes) and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can asparagus fern survive winter outside?

It can holiday outdoors in summer once nights are reliably above 5 °C, in shade or dappled light, hardened off gradually. Bring it back indoors well before the first autumn frost — do not wait for a frost warning, move it when nights drop toward 10-12 °C. It will never overwinter outside in a temperate climate; the indoors is its winter home, full stop.

What happens to asparagus fern below its minimum temperature?

Below about about 5 °C, growth stalls and the leaves start to show cold stress — dark, water-soaked, or yellowing patches. A single light frost blackens the foliage; a hard freeze kills the whole plant, roots included, and it does not recover. Even a cold, draughty windowsill or an unheated porch in winter can be enough to damage it permanently.