Cold hardiness & minimum temperature

Is Torenia fournieri 'Catalina Midnight Blue' (Torenia fournieri 'Catalina Midnight Blue')cold hardy? Hardiness zone & min temp

Also called Catalina Midnight Blue Wishbone Flower, Dark Blue Torenia.

More about torenia fournieri 'catalina midnight blue'

About Torenia fournieri 'Catalina Midnight Blue'

Torenia fournieri 'Catalina Midnight Blue' · also called Catalina Midnight Blue Wishbone Flower, Dark Blue Torenia · flowering

'Catalina Midnight Blue' is a trailing wishbone flower from the heat- and humidity-loving Catalina series, valued for its deep velvety midnight-blue, snapdragon-like blooms with paler throats. This shade-tolerant warm-season annual flowers continuously through summer, excels in containers and hanging baskets, and thrives where heat and moisture defeat many other bedding plants.

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

Watch for — Frost sensitivity: The plant dies at the first frost; plant out only after the soil has warmed and frost has passed.

What torenia fournieri 'catalina midnight blue''s hardiness rating actually means

Torenia fournieri 'Catalina Midnight Blue' 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 'Catalina Midnight Blue' shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for torenia fournieri 'catalina midnight blue' 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 'catalina midnight blue' 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 'catalina midnight blue' 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 'catalina midnight blue'

Torenia fournieri 'Catalina Midnight Blue' 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 'Catalina Midnight Blue' hardiness — frequently asked questions

Is torenia fournieri 'catalina midnight blue' cold hardy?

Torenia fournieri 'Catalina Midnight Blue' 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 'catalina midnight blue' 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 'catalina midnight blue' can survive?

What hardiness zone is torenia fournieri 'catalina midnight blue'?

Torenia fournieri 'Catalina Midnight Blue' 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 'catalina midnight blue' 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 'catalina midnight blue' 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.