Cold hardiness & minimum temperature

Is Black Prince snapdragon (Antirrhinum majus 'Black Prince')cold hardy? Hardiness zone & min temp

Also called Black Prince snapdragon, Dark snapdragon, Crimson snapdragon.

More about black prince snapdragon

About Black Prince snapdragon

Antirrhinum majus 'Black Prince' · also called Black Prince snapdragon, Dark snapdragon · flowering

Black Prince is a striking heirloom snapdragon with deep velvety crimson-red flowers contrasting against bronze-green, dark-flushed foliage. Growing 45–60 cm tall, it is a stand-out plant for gothic, monochrome, or jewel-toned borders and an excellent cut flower. It blooms in cool weather, performing best in spring and autumn in most climates.

Cold limit: USDA 7-10 · RHS H3 (7–21°C)

Watch for — Crown rot: Waterlogged soil at the crown causes rapid collapse. Plant in well-drained soil, avoid mulching too close to the stem base, and do not overwater. Particularly risky in cold, wet autumn or winter conditions.

What black prince snapdragon's hardiness rating actually means

Black Prince snapdragon is half-hardy (RHS H3). 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 H3 means: Half-hardy — comes through mild UK winters outside but is killed by a hard freeze. On the US scale that maps to USDA 7-10 — 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 −5 to 1 °C — a light, short frost only. Black Prince snapdragon shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for black prince snapdragon as it gets too cold:

Down to roughly about −5 to 1 °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 black prince snapdragon go outside or overwinter — and where?

It can live outside year-round only in the mildest, most sheltered part of USDA 7-10 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 black prince snapdragon can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H3 figure above.

Frost protection for borderline black prince snapdragon

Black Prince snapdragon 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.

Black Prince snapdragon hardiness — frequently asked questions

Is black prince snapdragon cold hardy?

Black Prince snapdragon is half-hardy (RHS H3). 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 7-10 (and sheltered UK gardens) black prince snapdragon can stay out; in colder areas it must be lifted, brought in, or treated as a frost-tender plant.

What is the minimum temperature black prince snapdragon can survive?

Minimum survivable temperature is roughly about −5 to 1 °C — a light, short frost only. Black Prince snapdragon shrugs off cold nights but a real, sustained freeze will kill it.

What hardiness zone is black prince snapdragon?

Black Prince snapdragon is rated USDA 7-10 and RHS H3 — Half-hardy — comes through mild UK winters outside but is killed by a hard freeze.

Can black prince snapdragon survive winter outside?

It can live outside year-round only in the mildest, most sheltered part of USDA 7-10 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 black prince snapdragon 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.