Cold hardiness & minimum temperature

Is Coleus (Coleus scutellarioides)cold hardy? Hardiness zone & min temp

Also called painted nettle, flame nettle, Plectranthus scutellarioides.

About Coleus

Coleus scutellarioides · also called painted nettle, flame nettle · flowering

Coleus is a tender perennial grown as a bedding annual or houseplant for its boldly patterned leaves in lime, burgundy, pink, and chocolate. Pinching keeps it bushy; flowering should be removed to extend foliage life. Mildly toxic to pets through essential oils.

Coleus scutellarioides (also placed in Plectranthus/Solenostemon), a mint-family (Lamiaceae) plant native to tropical and subtropical Asia through to northern Australia.

Grown for foliage, not bloom: pinch stem tips to keep it bushy and remove the blue-violet flower spikes promptly, since flowering and seed-set divert energy and can end the plant. Square stems mark its mint-family kinship. Foliage can cause allergic skin dermatitis on repeated contact.

Cold limit: USDA 10-11 (annual elsewhere) · RHS H1c (18-27°C)

Sources: plants.ces.ncsu.edu, missouribotanicalgarden.org, aspca.org

What coleus's hardiness rating actually means

Coleus 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 10-11 (annual 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 5 °C (and never frost). Coleus has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

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

Coleus hardiness — frequently asked questions

Is coleus cold hardy?

Coleus 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. Coleus can only live outside year-round in genuinely frost-free climates (roughly USDA 10-11 (annual elsewhere)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature coleus can survive?

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

What hardiness zone is coleus?

Coleus is rated USDA 10-11 (annual elsewhere) and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can coleus 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 coleus 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.