Cold hardiness & minimum temperature

Is Mexican Achimenes (Achimenes mexicana)cold hardy? Hardiness zone & min temp

Also called Mexican Achimenes, Mexican Magic Flower, Mexican Hot Water Plant.

More about mexican achimenes

About Mexican Achimenes

Achimenes mexicana · also called Mexican Achimenes, Mexican Magic Flower · tropical

Achimenes mexicana is a dwarf bushy magic flower from Mexico producing a profusion of blue-purple, trumpet-shaped flowers with white throats from early summer through October. One of the most reliable and floriferous species for indoor culture, it reaches just 20 cm and suits small pots and window boxes. Warmth, bright indirect light, and consistent moisture unlock its best performance.

Cold limit: USDA 10–12 · RHS H1b (20–28°C active growth (day); 17–19°C (night minimum); 13–15°C winter storage)

Watch for — Buds browning and not opening: The primary cause is night temperatures below 17°C (62°F). Keep the plant in a consistently warm room above 18°C at night during the growing season, away from cold windowsills.

What mexican achimenes's hardiness rating actually means

Mexican Achimenes 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 H1b means: Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season. On the US scale that maps to USDA 10–12 — 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 10 °C (sustained cold below this is damaging). Mexican Achimenes has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for mexican achimenes as it gets too cold:

Below about about 10 °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 mexican achimenes go outside or overwinter — and where?

It can holiday outdoors in summer once nights are reliably above 10 °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 mexican achimenes can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1b figure above.

Mexican Achimenes hardiness — frequently asked questions

Is mexican achimenes cold hardy?

Mexican Achimenes 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. Mexican Achimenes can only live outside year-round in genuinely frost-free climates (roughly USDA 10–12); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature mexican achimenes can survive?

What hardiness zone is mexican achimenes?

Mexican Achimenes is rated USDA 10–12 and RHS H1b — Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season.

Can mexican achimenes survive winter outside?

It can holiday outdoors in summer once nights are reliably above 10 °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 mexican achimenes below its minimum temperature?

Below about about 10 °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.