Cold hardiness & minimum temperature

Is Oklahoma Salmon zinnia (Zinnia elegans 'Oklahoma Salmon')cold hardy? Hardiness zone & min temp

Also called Oklahoma Salmon zinnia, Oklahoma Salmon.

More about oklahoma salmon zinnia

About Oklahoma Salmon zinnia

Zinnia elegans 'Oklahoma Salmon' · also called Oklahoma Salmon zinnia, Oklahoma Salmon · flowering

A heat-tolerant, mildew-resistant zinnia in the Oklahoma series, producing an abundance of medium-sized, fully double salmon-pink blooms on sturdy, branching stems ideal for cutting. Exceptionally productive in hot summers. A reliable choice for pollinator gardens, mixed borders, and florist-quality cut-flower beds throughout summer and into autumn.

Cold limit: USDA 2–11 (grown as annual) · RHS H1c (frost-tender annual) (18–38°C)

What oklahoma salmon zinnia's hardiness rating actually means

Oklahoma Salmon zinnia 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 2–11 (grown as 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 5 °C (and never frost). Oklahoma Salmon zinnia has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

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

Oklahoma Salmon zinnia hardiness — frequently asked questions

Is oklahoma salmon zinnia cold hardy?

Oklahoma Salmon zinnia 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. Oklahoma Salmon zinnia can only live outside year-round in genuinely frost-free climates (roughly USDA 2–11 (grown as annual)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature oklahoma salmon zinnia can survive?

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

What hardiness zone is oklahoma salmon zinnia?

Oklahoma Salmon zinnia is rated USDA 2–11 (grown as annual) and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can oklahoma salmon zinnia 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 oklahoma salmon zinnia 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.