Cold hardiness & minimum temperature

Is Poker alumroot (Heuchera cylindrica)cold hardy? Hardiness zone & min temp

Also called Poker alumroot, Roundleaf alumroot, Lava coral bells.

More about poker alumroot

About Poker alumroot

Heuchera cylindrica · also called Poker alumroot, Roundleaf alumroot · flowering

Heuchera cylindrica is a western North American native alumroot found on rocky slopes and cliff faces from British Columbia to Nevada. It produces distinctive cylindrical flower spikes of creamy-white to greenish-pink blooms in late spring, held well above rounded, dark-green foliage. Exceptionally drought-tolerant and suited to rock gardens and xeriscape plantings.

Cold limit: USDA 3–8 · RHS H7 (−29 °C to 38 °C)

Watch for — Crown exposure after frost heave: Shallow crowns heave out of the soil after freeze-thaw cycles. Press back into soil in spring and mulch with grit (not bark) to retain structure without trapping moisture.

What poker alumroot's hardiness rating actually means

Yes — poker alumroot is genuinely cold hardy. Rated RHS H7 and USDA 3–8, it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H7 means: Hardy in the severest European continental winters. On the US scale that maps to USDA 3–8 — 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 below about −20 °C. Poker alumroot is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for poker alumroot as it gets too cold:

It tolerates winter lows to about −20 °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 poker alumroot go outside or overwinter — and where?

Plant it out within USDA 3–8 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 poker alumroot can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

Poker alumroot hardiness — frequently asked questions

Is poker alumroot cold hardy?

Yes — poker alumroot is genuinely cold hardy. Rated RHS H7 and USDA 3–8, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Poker alumroot is hardy across USDA 3–8; 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 poker alumroot can survive?

Minimum survivable temperature is roughly below about −20 °C. Poker alumroot is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is poker alumroot?

Poker alumroot is rated USDA 3–8 and RHS H7 — Hardy in the severest European continental winters.

Can poker alumroot survive winter outside?

Plant it out within USDA 3–8 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 poker alumroot below its minimum temperature?

It tolerates winter lows to about −20 °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.