Cold hardiness & minimum temperature

Is Salvinia natans (Salvinia natans)cold hardy? Hardiness zone & min temp

Also called Floating Fern, Common Salvinia, Water Spangles.

More about salvinia natans

About Salvinia natans

Salvinia natans · also called Floating Fern, Common Salvinia · houseplant

Salvinia natans is a small free-floating fern with paired oval leaves covered in water-repellent hairs that keep it buoyant and dry on top. A submerged third leaf, finely divided, acts as a root substitute. Popular in aquariums and ponds for shade and shelter, it grows fast and should be thinned to prevent it from sealing the surface.

Cold limit: USDA 9-11 (frost-tender annual floater; overwinter indoors or treat as seasonal in cooler US zones) · RHS H2 (18-28°C)

Watch for — Browning patches: Result from cold snaps, nutrient depletion, or being trapped against equipment where they rot. Remove dead plants promptly to protect water quality.

What salvinia natans's hardiness rating actually means

Salvinia natans 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 9-11 (frost-tender annual floater; overwinter indoors or treat as seasonal in cooler US zones) — 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. Salvinia natans shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for salvinia natans 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 salvinia natans go outside or overwinter — and where?

It can live outside year-round only in the mildest, most sheltered part of USDA 9-11 (frost-tender annual floater; overwinter indoors or treat as seasonal in cooler US zones) 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 salvinia natans 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 salvinia natans

Salvinia natans 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.

Salvinia natans hardiness — frequently asked questions

Is salvinia natans cold hardy?

Salvinia natans 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 9-11 (frost-tender annual floater; overwinter indoors or treat as seasonal in cooler US zones) (and sheltered UK gardens) salvinia natans can stay out; in colder areas it must be lifted, brought in, or treated as a frost-tender plant.

What is the minimum temperature salvinia natans can survive?

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

What hardiness zone is salvinia natans?

Salvinia natans is rated USDA 9-11 (frost-tender annual floater; overwinter indoors or treat as seasonal in cooler US zones) and RHS H2 — Tender — survives a frost-free greenhouse or a very mild, sheltered spot.

Can salvinia natans survive winter outside?

It can live outside year-round only in the mildest, most sheltered part of USDA 9-11 (frost-tender annual floater; overwinter indoors or treat as seasonal in cooler US zones) 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 salvinia natans 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.