Cold hardiness & minimum temperature

Is Fringed Spurflower (Plectranthus ciliatus)cold hardy? Hardiness zone & min temp

Also called Fringed Spurflower, Speckled Spur Flower, Kirstenbosch Spurflower.

More about fringed spurflower

About Fringed Spurflower

Plectranthus ciliatus · also called Fringed Spurflower, Speckled Spur Flower · flowering

Plectranthus ciliatus is a sprawling to decumbent, aromatic perennial groundcover native to the subtropical forests and forest margins of KwaZulu-Natal and the Eastern Cape of South Africa, where it thrives in the dappled shade of the forest floor. It produces a low mound of dark green, softly hairy leaves with distinctive purple-fringed margins and pale pink to white flower spikes in late summer and autumn. The most important care fact is that it requires consistently moist, humus-rich soil and shade — it will not tolerate direct sun or drought for prolonged periods. Not individually listed by ASPCA; treat as mildly toxic due to its aromatic essential oil content.

Cold limit: USDA 10a–11b (indoor in most climates) · RHS H2 (10–28°C)

What fringed spurflower's hardiness rating actually means

Fringed Spurflower is half-hardy (RHS H2). 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 H2 means: Tender — survives a frost-free greenhouse or a very mild, sheltered spot. On the US scale that maps to USDA 10a–11b (indoor in most climates) — 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 1 to 5 °C — tolerates cold but no real frost. Fringed Spurflower shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for fringed spurflower as it gets too cold:

Down to roughly about 1 to 5 °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 fringed spurflower go outside or overwinter — and where?

It can live outside year-round only in the mildest, most sheltered part of USDA 10a–11b (indoor in most climates) 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 fringed spurflower can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H2 figure above.

Frost protection for borderline fringed spurflower

Fringed Spurflower 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.

Fringed Spurflower hardiness — frequently asked questions

Is fringed spurflower cold hardy?

Fringed Spurflower is half-hardy (RHS H2). 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 10a–11b (indoor in most climates) (and sheltered UK gardens) fringed spurflower can stay out; in colder areas it must be lifted, brought in, or treated as a frost-tender plant.

What is the minimum temperature fringed spurflower can survive?

Minimum survivable temperature is roughly about 1 to 5 °C — tolerates cold but no real frost. Fringed Spurflower shrugs off cold nights but a real, sustained freeze will kill it.

What hardiness zone is fringed spurflower?

Fringed Spurflower is rated USDA 10a–11b (indoor in most climates) and RHS H2 — Tender — survives a frost-free greenhouse or a very mild, sheltered spot.

Can fringed spurflower survive winter outside?

It can live outside year-round only in the mildest, most sheltered part of USDA 10a–11b (indoor in most climates) 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 fringed spurflower 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.