Cold hardiness & minimum temperature

Is Spike Moss (Selaginella kraussiana)cold hardy? Hardiness zone & min temp

Also called Spike moss, Krauss' clubmoss, Krauss' spikemoss, African clubmoss, Japanese moss, Trailing Irish moss, Spreading club moss.

More about spike moss

About Spike Moss

Selaginella kraussiana · also called Spike moss, Krauss' clubmoss · houseplant

Spike moss (Selaginella kraussiana) is a low, creeping fern relative grown for its fine, feathery emerald foliage and mat-forming habit, ideal for terrariums. It demands constant moisture, very high humidity, and shade from direct sun. The ASPCA lists it as non-toxic to dogs, cats, and horses, making it pet-safe.

Cold limit: USDA 11a-12b (frost-tender tropical perennial; grown as a houseplant or terrarium plant elsewhere) (18-24°C)

What spike moss's hardiness rating actually means

Spike Moss 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 H1b means: Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season. On the US scale that maps to USDA 11a-12b (frost-tender tropical perennial; grown as a houseplant or terrarium plant elsewhere) — 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 10 °C (sustained cold below this is damaging). Spike Moss has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for spike moss as it gets too cold:

Below about about 10 °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 spike moss go outside or overwinter — and where?

It can holiday outdoors in summer once nights are reliably above 10 °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 spike moss can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1b figure above.

Spike Moss hardiness — frequently asked questions

Is spike moss cold hardy?

Spike Moss 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. Spike Moss can only live outside year-round in genuinely frost-free climates (roughly USDA 11a-12b (frost-tender tropical perennial; grown as a houseplant or terrarium plant elsewhere)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature spike moss can survive?

Minimum survivable temperature is roughly about 10 °C (sustained cold below this is damaging). Spike Moss has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

What hardiness zone is spike moss?

Spike Moss is rated USDA 11a-12b (frost-tender tropical perennial; grown as a houseplant or terrarium plant elsewhere) and RHS H1b — Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season.

Can spike moss survive winter outside?

It can holiday outdoors in summer once nights are reliably above 10 °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 spike moss below its minimum temperature?

Below about about 10 °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.