Cold hardiness & minimum temperature

Is Pelargonium 'Mystery' (Pelargonium 'Mystery')cold hardy? Hardiness zone & min temp

Also called Mystery unique pelargonium.

More about pelargonium 'mystery'

About Pelargonium 'Mystery'

Pelargonium 'Mystery' · also called Mystery unique pelargonium · flowering

A Unique-group pelargonium with deep velvety burgundy-red flowers marked darker at the centre, carried over aromatic, roughly cut foliage. Shrubby, vigorous and long-flowering, it makes a striking specimen in large pots and conservatories. As a tender pelargonium it requires full sun, sharply drained compost and frost-free winter shelter to flower freely each season.

Cold limit: USDA 9-11 (tender; overwinter frost-free) · RHS H1c (10-24°C)

Watch for — Reluctant flowering: Too little sun or an unpruned plant produces leaves over flowers. Move to full sun and prune in late winter to stimulate flowering wood.

What pelargonium 'mystery''s hardiness rating actually means

Pelargonium 'Mystery' 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 9-11 (tender; overwinter frost-free) — 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). Pelargonium 'Mystery' has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for pelargonium 'mystery' 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 pelargonium 'mystery' 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 pelargonium 'mystery' can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1c figure above.

Pelargonium 'Mystery' hardiness — frequently asked questions

Is pelargonium 'mystery' cold hardy?

Pelargonium 'Mystery' 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. Pelargonium 'Mystery' can only live outside year-round in genuinely frost-free climates (roughly USDA 9-11 (tender; overwinter frost-free)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature pelargonium 'mystery' can survive?

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

What hardiness zone is pelargonium 'mystery'?

Pelargonium 'Mystery' is rated USDA 9-11 (tender; overwinter frost-free) and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can pelargonium 'mystery' 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 pelargonium 'mystery' 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.