Cold hardiness & minimum temperature

Is Gloxinia sylvatica (Gloxinia sylvatica)cold hardy? Hardiness zone & min temp

Also called Bolivian sunset, forest gloxinia.

More about gloxinia sylvatica

About Gloxinia sylvatica

Gloxinia sylvatica · also called Bolivian sunset, forest gloxinia · flowering

Gloxinia sylvatica, the Bolivian sunset gloxinia (now often Seemannia sylvatica), is a graceful gesneriad bearing slender tubular orange-red flowers above narrow, willowy green leaves. It spreads by scaly rhizomes, blooms heavily in autumn and winter, and is among the easiest and hardiest gloxinia relatives, tolerating cooler conditions than most of its tropical kin.

Cold limit: USDA 8-10 (rhizomes survive light frost with mulch; usually grown frost-free) · RHS H2 (15-25°C)

Watch for — Rhizome rot: Cold, waterlogged soil quickly rots the rhizomes. Use a fast-draining mix, water sparingly in dormancy, and avoid standing water.

What gloxinia sylvatica's hardiness rating actually means

Gloxinia sylvatica 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 8-10 (rhizomes survive light frost with mulch; usually grown frost-free) — 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. Gloxinia sylvatica shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for gloxinia sylvatica 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 gloxinia sylvatica go outside or overwinter — and where?

It can live outside year-round only in the mildest, most sheltered part of USDA 8-10 (rhizomes survive light frost with mulch; usually grown frost-free) 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 gloxinia sylvatica 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 gloxinia sylvatica

Gloxinia sylvatica 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.

Gloxinia sylvatica hardiness — frequently asked questions

Is gloxinia sylvatica cold hardy?

Gloxinia sylvatica 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 8-10 (rhizomes survive light frost with mulch; usually grown frost-free) (and sheltered UK gardens) gloxinia sylvatica can stay out; in colder areas it must be lifted, brought in, or treated as a frost-tender plant.

What is the minimum temperature gloxinia sylvatica can survive?

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

What hardiness zone is gloxinia sylvatica?

Gloxinia sylvatica is rated USDA 8-10 (rhizomes survive light frost with mulch; usually grown frost-free) and RHS H2 — Tender — survives a frost-free greenhouse or a very mild, sheltered spot.

Can gloxinia sylvatica survive winter outside?

It can live outside year-round only in the mildest, most sheltered part of USDA 8-10 (rhizomes survive light frost with mulch; usually grown frost-free) 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 gloxinia sylvatica 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.