Cold hardiness & minimum temperature

Is Sinningia tubiflora (Sinningia tubiflora)cold hardy? Hardiness zone & min temp

Also called white sinningia, tube-flowered sinningia.

More about sinningia tubiflora

About Sinningia tubiflora

Sinningia tubiflora · also called white sinningia, tube-flowered sinningia · flowering

Sinningia tubiflora is a tuberous South American gesneriad grown for tall stems of fragrant, long-tubed white flowers above soft, hairy green leaves. It spreads by underground tubers, blooms in summer, and dies back to rest over winter. Give it bright indirect light, warmth and steady moisture in the growing season for the heaviest, scented flush.

Cold limit: USDA 8-10 (root-hardy in mild zones; grown as a frost-tender container plant elsewhere) · RHS H2 (18-27°C)

Watch for — Spotted or marked leaves: Cold water or droplets sitting on the hairy foliage cause pale blotches. Water the soil, not the leaves, using room-temperature water.

What sinningia tubiflora's hardiness rating actually means

Sinningia tubiflora 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 (root-hardy in mild zones; grown as a frost-tender container plant 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 1 to 5 °C — tolerates cold but no real frost. Sinningia tubiflora shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for sinningia tubiflora 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 sinningia tubiflora go outside or overwinter — and where?

It can live outside year-round only in the mildest, most sheltered part of USDA 8-10 (root-hardy in mild zones; grown as a frost-tender container plant elsewhere) 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 sinningia tubiflora 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 sinningia tubiflora

Sinningia tubiflora 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.

Sinningia tubiflora hardiness — frequently asked questions

Is sinningia tubiflora cold hardy?

Sinningia tubiflora 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 (root-hardy in mild zones; grown as a frost-tender container plant elsewhere) (and sheltered UK gardens) sinningia tubiflora can stay out; in colder areas it must be lifted, brought in, or treated as a frost-tender plant.

What is the minimum temperature sinningia tubiflora can survive?

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

What hardiness zone is sinningia tubiflora?

Sinningia tubiflora is rated USDA 8-10 (root-hardy in mild zones; grown as a frost-tender container plant elsewhere) and RHS H2 — Tender — survives a frost-free greenhouse or a very mild, sheltered spot.

Can sinningia tubiflora survive winter outside?

It can live outside year-round only in the mildest, most sheltered part of USDA 8-10 (root-hardy in mild zones; grown as a frost-tender container plant elsewhere) 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 sinningia tubiflora 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.