Cold hardiness & minimum temperature

Is Orange King Calendula (Calendula officinalis 'Orange King')cold hardy? Hardiness zone & min temp

Also called Pot Marigold, English Marigold, Scotch Marigold.

More about orange king calendula

About Orange King Calendula

Calendula officinalis 'Orange King' · also called Pot Marigold, English Marigold · herb

Orange King Calendula is a showy, fully double-flowered variety of pot marigold bearing rich tangerine-orange blooms. Widely grown for cut flowers, edible petals, and skin-care preparations. Easy to grow in full sun. Mildly toxic to pets — saponins and triterpenoids can cause GI upset.

Cold limit: USDA 9-11 (grown as cool-season annual elsewhere) · RHS H4 (7-25°C)

Watch for — Ceasing to flower in heat: Blooming slows or stops above 25°C. Shear plants back by a third and they will flush again when temperatures cool.

What orange king calendula's hardiness rating actually means

Hardiness works differently for orange king calendula: it is grown as a seasonal crop, not overwintered. The question is not "what zone" but "how long is your frost-free growing window". Its RHS rating of H4 means: Hardy in an average winter across much of the temperate world. On the US scale that maps to USDA 9-11 (grown as cool-season annual elsewhere) — 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

As an annual crop, its "minimum temperature" is the first hard frost — that is the end of the plant's life, not a survivable low. Many types are also damaged by light frost (around 0 °C).

Concretely, for orange king calendula as it gets too cold:

Light frost (around 0 to −2 °C) damages or kills tender summer crops outright; cold-hardy types take a few degrees of frost.
The plant does not "survive winter" — its life cycle simply ends, by design, when frost arrives or it finishes cropping.
A surprise late spring frost can also kill young transplants set out too early, before the season even starts.

Can orange king calendula go outside or overwinter — and where?

Time it to your frost dates: sow or plant out after the last spring frost, and aim to harvest before the first autumn frost.
In short-season zones, start it indoors or under cover to stretch the effective growing window.
Hardier crops in this group can be sown for an autumn or overwintered harvest in mild zones — check the specific crop.

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 orange king calendula can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H4 figure above.

Frost protection for borderline orange king calendula

Orange King Calendula is right on a hardiness edge in many gardens, so if you are pushing it, these measures buy it the margin it needs:

Use fleece, cloches or a cold frame at each end of the season to dodge a borderline frost and add growing weeks.
Have row cover ready for an unexpected late spring or early autumn frost.
Know your local last- and first-frost dates and count back the crop’s days-to-maturity to schedule the sowing.

Orange King Calendula hardiness — frequently asked questions

Is orange king calendula cold hardy?

Hardiness works differently for orange king calendula: it is grown as a seasonal crop, not overwintered. The question is not "what zone" but "how long is your frost-free growing window". A seasonal crop, not a perennial. Orange King Calendula is grown 9-11 (grown as cool-season annual elsewhere); you sow after the last frost and harvest before the first one, then start again next year.

What is the minimum temperature orange king calendula can survive?

As an annual crop, its "minimum temperature" is the first hard frost — that is the end of the plant's life, not a survivable low. Many types are also damaged by light frost (around 0 °C).

What hardiness zone is orange king calendula?

Orange King Calendula is rated USDA 9-11 (grown as cool-season annual elsewhere) and RHS H4 — Hardy in an average winter across much of the temperate world.

Can orange king calendula survive winter outside?

Time it to your frost dates: sow or plant out after the last spring frost, and aim to harvest before the first autumn frost. In short-season zones, start it indoors or under cover to stretch the effective growing window. Hardier crops in this group can be sown for an autumn or overwintered harvest in mild zones — check the specific crop.

How do I protect orange king calendula from frost?

Use fleece, cloches or a cold frame at each end of the season to dodge a borderline frost and add growing weeks. Have row cover ready for an unexpected late spring or early autumn frost. Know your local last- and first-frost dates and count back the crop’s days-to-maturity to schedule the sowing.