Cold hardiness & minimum temperature

Is Torenia fournieri 'Summer Wave Large Violet' (Torenia fournieri 'Summer Wave Large Violet')cold hardy? Hardiness zone & min temp

Also called Summer Wave Violet Wishbone Flower, Trailing Violet Torenia.

More about torenia fournieri 'summer wave large violet'

About Torenia fournieri 'Summer Wave Large Violet'

Torenia fournieri 'Summer Wave Large Violet' · also called Summer Wave Violet Wishbone Flower, Trailing Violet Torenia · flowering

'Summer Wave Large Violet' is a vigorous, large-flowered trailing wishbone flower in the Summer Wave series, smothered in violet-blue, throated blooms all summer. Bred for spreading habit and heat tolerance, it shines in hanging baskets and containers, thrives in shade and humidity, and flowers non-stop until frost without needing deadheading.

Cold limit: USDA 2-11 (frost-tender warm-season annual) · RHS H2 (18-29°C)

What torenia fournieri 'summer wave large violet''s hardiness rating actually means

Torenia fournieri 'Summer Wave Large Violet' 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 2-11 (frost-tender warm-season annual) — 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. Torenia fournieri 'Summer Wave Large Violet' shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for torenia fournieri 'summer wave large violet' 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 torenia fournieri 'summer wave large violet' go outside or overwinter — and where?

It can live outside year-round only in the mildest, most sheltered part of USDA 2-11 (frost-tender warm-season annual) 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 torenia fournieri 'summer wave large violet' 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 torenia fournieri 'summer wave large violet'

Torenia fournieri 'Summer Wave Large Violet' 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.

Torenia fournieri 'Summer Wave Large Violet' hardiness — frequently asked questions

Is torenia fournieri 'summer wave large violet' cold hardy?

Torenia fournieri 'Summer Wave Large Violet' 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 2-11 (frost-tender warm-season annual) (and sheltered UK gardens) torenia fournieri 'summer wave large violet' can stay out; in colder areas it must be lifted, brought in, or treated as a frost-tender plant.

What is the minimum temperature torenia fournieri 'summer wave large violet' can survive?

What hardiness zone is torenia fournieri 'summer wave large violet'?

Torenia fournieri 'Summer Wave Large Violet' is rated USDA 2-11 (frost-tender warm-season annual) and RHS H2 — Tender — survives a frost-free greenhouse or a very mild, sheltered spot.

Can torenia fournieri 'summer wave large violet' survive winter outside?

It can live outside year-round only in the mildest, most sheltered part of USDA 2-11 (frost-tender warm-season annual) 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 torenia fournieri 'summer wave large violet' 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.