Cold hardiness & minimum temperature

Is Persian Carpet zinnia (Zinnia haageana 'Persian Carpet')cold hardy? Hardiness zone & min temp

Also called Persian Carpet zinnia, Mexican zinnia, Persian Carpet.

More about persian carpet zinnia

About Persian Carpet zinnia

Zinnia haageana 'Persian Carpet' · also called Persian Carpet zinnia, Mexican zinnia · flowering

A charming annual zinnia species from Mexico bearing small, richly bicolored double and semi-double blooms in combinations of mahogany, orange, cream, and yellow — resembling woven carpet patterns. More heat- and drought-tolerant than Z. elegans, with excellent mildew resistance. Perfect for cottage borders, containers, and butterfly gardens.

Cold limit: USDA 2–11 (grown as annual) · RHS H1c (frost-tender annual) (18–40°C)

Watch for — Poor germination in cold soil: Seeds rot rather than germinate if sown into soil below 18°C (65°F). Wait until soil is reliably warm, or pre-warm beds with black plastic. Germination is rapid (5–7 days) once conditions are correct.

What persian carpet zinnia's hardiness rating actually means

Persian Carpet 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). Persian Carpet zinnia has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

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

Persian Carpet zinnia hardiness — frequently asked questions

Is persian carpet zinnia cold hardy?

Persian Carpet 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. Persian Carpet 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 persian carpet zinnia can survive?

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

What hardiness zone is persian carpet zinnia?

Persian Carpet 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 persian carpet 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 persian carpet 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.