Cold hardiness & minimum temperature

Is Muster-John-Henry (Tagetes minuta)cold hardy? Hardiness zone & min temp

Also called Muster-John-Henry, southern cone marigold, Mexican marigold, wild marigold, southern marigold.

More about muster-john-henry

About Muster-John-Henry

Tagetes minuta · also called Muster-John-Henry, southern cone marigold · flowering

A tall, strongly aromatic annual from South America grown primarily as a companion plant and biological soil improver rather than for ornamental display. Its small, creamy-yellow flower heads are modest, but root secretions powerfully suppress soil nematodes and some weeds. The foliage yields an essential oil used in perfumery. Exceptionally vigorous in warm conditions, reaching 2 m in a single season.

Cold limit: USDA 8-11 · RHS H1c (15–35°C)

Watch for — Frost sensitive: Plants are killed by the first autumn frost. In cool climates, start seed indoors 4–6 weeks before the last frost to maximise the growing season and nematode-suppression window.

What muster-john-henry's hardiness rating actually means

Muster-John-Henry 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 8-11 — 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). Muster-John-Henry has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for muster-john-henry 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 muster-john-henry 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 muster-john-henry can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1c figure above.

Muster-John-Henry hardiness — frequently asked questions

Is muster-john-henry cold hardy?

Muster-John-Henry 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. Muster-John-Henry can only live outside year-round in genuinely frost-free climates (roughly USDA 8-11); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature muster-john-henry can survive?

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

What hardiness zone is muster-john-henry?

Muster-John-Henry is rated USDA 8-11 and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can muster-john-henry 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 muster-john-henry 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.