Cold hardiness & minimum temperature

Is Watch Chain Plant (Crassula muscosa)cold hardy? Hardiness zone & min temp

Also called Watch chain plant, Princess pine, Rattail crassula, Zipper plant, Clubmoss crassula.

More about watch chain plant

About Watch Chain Plant

Crassula muscosa · also called Watch chain plant, Princess pine · houseplant

The watch chain plant (Crassula muscosa) is a quirky South African succulent whose stems are hidden by tightly stacked, scale-like green leaves resembling a zipper. Give it bright light, gritty fast-draining soil, and water only when bone dry. It is not ASPCA-listed but its genus includes toxic jade, so treat as mildly toxic.

Cold limit: USDA 9b-11 (12-26 C)

Watch for — Cold or frost damage: Not frost-hardy. Temperatures below about 10 C (50 F) cause yellowing and tissue damage, so overwinter indoors in cold climates.

What watch chain plant's hardiness rating actually means

Watch Chain Plant 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 9b-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 10 °C (sustained cold below this is damaging). Watch Chain Plant has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for watch chain plant 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 watch chain plant 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 watch chain plant can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1b figure above.

Watch Chain Plant hardiness — frequently asked questions

Is watch chain plant cold hardy?

Watch Chain Plant 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. Watch Chain Plant can only live outside year-round in genuinely frost-free climates (roughly USDA 9b-11); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature watch chain plant can survive?

What hardiness zone is watch chain plant?

Watch Chain Plant is rated USDA 9b-11 and RHS H1b — Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season.

Can watch chain plant 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 watch chain plant 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.