Cold hardiness & minimum temperature

Is Claret Cup Cactus (Echinocereus triglochidiatus)cold hardy? Hardiness zone & min temp

Also called Claret Cup Cactus, Kingcup Cactus, Scarlet Hedgehog Cactus.

More about claret cup cactus

About Claret Cup Cactus

Echinocereus triglochidiatus · also called Claret Cup Cactus, Kingcup Cactus · houseplant

Echinocereus triglochidiatus is a clumping hedgehog cactus native to the American Southwest and northern Mexico, prized for its spectacular clusters of brilliant scarlet to orange-red, hummingbird-pollinated flowers in spring. Exceptionally cold-hardy for a cactus, it is among the easiest Echinocereus to grow, tolerating frost outdoors and thriving in sunny spots indoors.

Cold limit: USDA 5-10 · RHS H5 (-20–38°C)

Watch for — Failure to flower without winter cold: Consistent warmth year-round inhibits flower bud formation. This cold-hardy species needs a genuine cool-to-cold, dry winter rest — ideally 2–3 months at 0–10°C (32–50°F) — to trigger its spectacular spring bloom. Move outdoor pots to an unheated greenhouse or cold frame.

What claret cup cactus's hardiness rating actually means

Yes — claret cup cactus is genuinely cold hardy. Rated RHS H5 and USDA 5-10, it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H5 means: Hardy in most of the UK and in cold winters. On the US scale that maps to USDA 5-10 — 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 −15 to −10 °C. Claret Cup Cactus is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for claret cup cactus as it gets too cold:

It tolerates winter lows to about −15 to −10 °C once established.
Below its rated zone, the visible damage is browned or blackened top growth and, in the worst case, a killed crown or root.
First-year, newly planted, or container-grown specimens are noticeably less hardy than established garden plants — the roots are exposed.

Can claret cup cactus go outside or overwinter — and where?

Plant it out within USDA 5-10 and it overwinters with little or no help.
It does not want to come indoors — a warm winter room actually weakens a hardy plant by denying it dormancy.
The real risks in its range are waterlogging, wind-rock on young plants, and a late hard frost on new growth — not ordinary winter cold.

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 claret cup cactus can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H5 figure above.

Claret Cup Cactus hardiness — frequently asked questions

Is claret cup cactus cold hardy?

Yes — claret cup cactus is genuinely cold hardy. Rated RHS H5 and USDA 5-10, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Claret Cup Cactus is hardy across USDA 5-10; it belongs in the ground or a frost-proof container, not on a windowsill, and many types actively need a cold winter to perform.

What is the minimum temperature claret cup cactus can survive?

Minimum survivable temperature is roughly about −15 to −10 °C. Claret Cup Cactus is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is claret cup cactus?

Claret Cup Cactus is rated USDA 5-10 and RHS H5 — Hardy in most of the UK and in cold winters.

Can claret cup cactus survive winter outside?

Plant it out within USDA 5-10 and it overwinters with little or no help. It does not want to come indoors — a warm winter room actually weakens a hardy plant by denying it dormancy. The real risks in its range are waterlogging, wind-rock on young plants, and a late hard frost on new growth — not ordinary winter cold.

What happens to claret cup cactus below its minimum temperature?

It tolerates winter lows to about −15 to −10 °C once established. Below its rated zone, the visible damage is browned or blackened top growth and, in the worst case, a killed crown or root. First-year, newly planted, or container-grown specimens are noticeably less hardy than established garden plants — the roots are exposed.