Cold hardiness & minimum temperature

Is Persian Shield (Strobilanthes dyerianus)cold hardy? Hardiness zone & min temp

Also called Persian Shield, Royal Purple Plant, Persian shield plant.

More about persian shield

About Persian Shield

Strobilanthes dyerianus · also called Persian Shield, Royal Purple Plant · flowering

Persian Shield is a tropical foliage perennial grown for iridescent purple-silver, lance-shaped leaves. Give it bright indirect light, consistently moist (never soggy) soil, warm temperatures and high humidity. Not individually listed by the ASPCA, so treat it as mildly toxic and check with your vet before exposing pets.

Cold limit: USDA USDA 10-11 (RHS H1B; tender, grown as a houseplant or summer annual elsewhere) (18-24°C)

What persian shield's hardiness rating actually means

Persian Shield is not cold hardy. It is a tropical houseplant that dies if it is left out through frost — there is no zone where it overwinters outdoors in a UK or cold-US climate. Its RHS rating of H1c means: Warm-temperate — can summer outdoors but must come in well before the first frost. On the US scale that maps to USDA USDA 10-11 (RHS H1B; tender, grown as a houseplant or summer annual 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 5 °C (and never frost). Persian Shield has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for persian shield as it gets too cold:

Below about about 5 °C, growth stalls and the leaves start to show cold stress — dark, water-soaked, or yellowing patches.
A single light frost blackens the foliage; a hard freeze kills the whole plant, roots included, and it does not recover.
Even a cold, draughty windowsill or an unheated porch in winter can be enough to damage it permanently.

Can persian shield go outside or overwinter — and where?

It can holiday outdoors in summer once nights are reliably above 5 °C, in shade or dappled light, hardened off gradually.
Bring it back indoors well before the first autumn frost — do not wait for a frost warning, move it when nights drop toward 10-12 °C.
It will never overwinter outside in a temperate climate; the indoors is its winter home, full stop.

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 persian shield can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1c figure above.

Persian Shield hardiness — frequently asked questions

Is persian shield cold hardy?

Persian Shield is not cold hardy. It is a tropical houseplant that dies if it is left out through frost — there is no zone where it overwinters outdoors in a UK or cold-US climate. Indoor-only in almost every home. Persian Shield can only live outside year-round in genuinely frost-free climates (roughly USDA USDA 10-11 (RHS H1B; tender, grown as a houseplant or summer annual elsewhere)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature persian shield can survive?

Minimum survivable temperature is roughly about 5 °C (and never frost). Persian Shield has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

What hardiness zone is persian shield?

Persian Shield is rated USDA USDA 10-11 (RHS H1B; tender, grown as a houseplant or summer annual elsewhere) and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can persian shield survive winter outside?

It can holiday outdoors in summer once nights are reliably above 5 °C, in shade or dappled light, hardened off gradually. Bring it back indoors well before the first autumn frost — do not wait for a frost warning, move it when nights drop toward 10-12 °C. It will never overwinter outside in a temperate climate; the indoors is its winter home, full stop.

What happens to persian shield below its minimum temperature?

Below about about 5 °C, growth stalls and the leaves start to show cold stress — dark, water-soaked, or yellowing patches. A single light frost blackens the foliage; a hard freeze kills the whole plant, roots included, and it does not recover. Even a cold, draughty windowsill or an unheated porch in winter can be enough to damage it permanently.