Cold hardiness & minimum temperature

Is Scarlet Freesia (Freesia laxa)cold hardy? Hardiness zone & min temp

Also called Scarlet Freesia, False Freesia, Flowering Grass.

More about scarlet freesia

About Scarlet Freesia

Freesia laxa · also called Scarlet Freesia, False Freesia · flowering

Freesia laxa (syn. Anomatheca laxa) is a slender, graceful South African cormous perennial producing bright scarlet-red, six-petalled flowers on wiry stems from May to June. Easier and hardier than florist freesias, it self-seeds freely, naturalizes in gravel gardens, and thrives in full sun with excellent drainage. The pure-white form (var. alba) is equally appealing.

Cold limit: USDA 8-10 · RHS H3 (-5 to 25°C (frost-hardy to about -5°C in sheltered positions))

Watch for — Corm rot in wet winters: In the UK, corms left in wet, cold soil risk rotting over winter in all but the mildest gardens (RHS H3 means marginal outdoors). In colder areas or on heavy soils, lift corms after flowering, dry them off, and store frost-free until spring replanting.

What scarlet freesia's hardiness rating actually means

Scarlet Freesia is half-hardy (RHS H3). 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 H3 means: Half-hardy — comes through mild UK winters outside but is killed by a hard freeze. On the US scale that maps to USDA 8-10 — 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 to 1 °C — a light, short frost only. Scarlet Freesia shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for scarlet freesia as it gets too cold:

Down to roughly about −5 to 1 °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 scarlet freesia go outside or overwinter — and where?

It can live outside year-round only in the mildest, most sheltered part of USDA 8-10 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 scarlet freesia can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H3 figure above.

Frost protection for borderline scarlet freesia

Scarlet Freesia 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.

Scarlet Freesia hardiness — frequently asked questions

Is scarlet freesia cold hardy?

Scarlet Freesia is half-hardy (RHS H3). 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 8-10 (and sheltered UK gardens) scarlet freesia can stay out; in colder areas it must be lifted, brought in, or treated as a frost-tender plant.

What is the minimum temperature scarlet freesia can survive?

Minimum survivable temperature is roughly about −5 to 1 °C — a light, short frost only. Scarlet Freesia shrugs off cold nights but a real, sustained freeze will kill it.

What hardiness zone is scarlet freesia?

Scarlet Freesia is rated USDA 8-10 and RHS H3 — Half-hardy — comes through mild UK winters outside but is killed by a hard freeze.

Can scarlet freesia survive winter outside?

It can live outside year-round only in the mildest, most sheltered part of USDA 8-10 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 scarlet freesia 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.