Cold hardiness & minimum temperature

Is Mackay's Zygopetalum (Zygopetalum mackayi)cold hardy? Hardiness zone & min temp

Also called Blue Orchid, Zygo Orchid, Mackay's Zygo.

More about mackay's zygopetalum

About Mackay's Zygopetalum

Zygopetalum mackayi · also called Blue Orchid, Zygo Orchid · tropical

Zygopetalum mackayi is a striking Brazilian epiphyte producing tall spikes of large, heavily fragrant flowers with marbled green and brown petals and a vivid violet-veined white lip. It grows best in intermediate temperatures with good light and a defined dry rest in winter. Orchidaceae; pet-safe.

Cold limit: USDA 10-11 (indoor-only in most US climates) · RHS H1c (13-25°C)

Watch for — Failure to spike: Requires a cooler, drier winter rest (nights 13-15°C) for 6-8 weeks. Move to a cooler room or reduce heating at night in autumn.

What mackay's zygopetalum's hardiness rating actually means

Mackay's Zygopetalum 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 10-11 (indoor-only in most US climates) — 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). Mackay's Zygopetalum has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

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

Mackay's Zygopetalum hardiness — frequently asked questions

Is mackay's zygopetalum cold hardy?

Mackay's Zygopetalum 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. Mackay's Zygopetalum can only live outside year-round in genuinely frost-free climates (roughly USDA 10-11 (indoor-only in most US climates)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature mackay's zygopetalum can survive?

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

What hardiness zone is mackay's zygopetalum?

Mackay's Zygopetalum is rated USDA 10-11 (indoor-only in most US climates) and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can mackay's zygopetalum 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 mackay's zygopetalum 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.