Cold hardiness & minimum temperature

Is Tweedy's Lewisia (Lewisia tweedyi)cold hardy? Hardiness zone & min temp

Also called Tweedy's Lewisia, Tweedy Lewisia.

More about tweedy's lewisia

About Tweedy's Lewisia

Lewisia tweedyi · also called Tweedy's Lewisia, Tweedy Lewisia · flowering

A large, spectacular Lewisia from alpine rocky slopes in the Cascade and Wenatchee mountains of Washington State, bearing big peach-to-apricot or pale pink flowers in spring. One of the most striking alpine plants, yet demanding: it requires perfect drainage, cool summers, a dry rest period, and protection from winter wet.

Cold limit: USDA 4–7 · RHS H5 (-15 to 22°C)

Watch for — Winter and summer crown rot: Far more common in cultivation than in the wild due to excess moisture. Plant in a vertical crevice or angled in a trough, protect from prolonged rain, and ensure perfect drainage at all times.

What tweedy's lewisia's hardiness rating actually means

Yes — tweedy's lewisia is genuinely cold hardy. Rated RHS H5 and USDA 4–7, 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 4–7 — 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. Tweedy's Lewisia is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for tweedy's lewisia 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 tweedy's lewisia go outside or overwinter — and where?

Plant it out within USDA 4–7 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 tweedy's lewisia can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H5 figure above.

Tweedy's Lewisia hardiness — frequently asked questions

Is tweedy's lewisia cold hardy?

Yes — tweedy's lewisia is genuinely cold hardy. Rated RHS H5 and USDA 4–7, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Tweedy's Lewisia is hardy across USDA 4–7; 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 tweedy's lewisia can survive?

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

What hardiness zone is tweedy's lewisia?

Tweedy's Lewisia is rated USDA 4–7 and RHS H5 — Hardy in most of the UK and in cold winters.

Can tweedy's lewisia survive winter outside?

Plant it out within USDA 4–7 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 tweedy's lewisia 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.