Cold hardiness & minimum temperature

Is Canadian Lousewort (Pedicularis canadensis)cold hardy? Hardiness zone & min temp

Also called Canadian lousewort, Wood betony, Forest lousewort, Lousewort.

More about canadian lousewort

About Canadian Lousewort

Pedicularis canadensis · also called Canadian lousewort, Wood betony · flowering

Pedicularis canadensis is a spring-blooming hemiparasitic perennial native to open woodlands, prairie edges, and mesic forests from Quebec and Manitoba south through the eastern US to Texas and Florida. Its finely divided, fernlike foliage and tight spikes of hooded yellow to reddish-purple flowers emerge from April through June; it taps the roots of surrounding grasses and forbs for supplemental water and minerals while still photosynthesising its own sugars. Because it is a hemiparasite, it must be grown alongside suitable host plants — native bunchgrasses and prairie forbs are ideal — and it resents transplanting once established. It contains alkaloids and phenylpropanoid glycosides and is classified as mildly toxic to pets.

Cold limit: USDA 4-8 · RHS H6 (-28 to 32 °C)

What canadian lousewort's hardiness rating actually means

Yes — canadian lousewort is genuinely cold hardy. Rated RHS H6 and USDA 4-8, it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H6 means: Hardy throughout the UK and northern Europe. On the US scale that maps to USDA 4-8 — 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 about −20 to −15 °C. Canadian Lousewort is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for canadian lousewort as it gets too cold:

It tolerates winter lows to about −20 to −15 °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 canadian lousewort go outside or overwinter — and where?

Plant it out within USDA 4-8 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 canadian lousewort can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H6 figure above.

Canadian Lousewort hardiness — frequently asked questions

Is canadian lousewort cold hardy?

Yes — canadian lousewort is genuinely cold hardy. Rated RHS H6 and USDA 4-8, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Canadian Lousewort is hardy across USDA 4-8; 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 canadian lousewort can survive?

Minimum survivable temperature is roughly about −20 to −15 °C. Canadian Lousewort is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is canadian lousewort?

Canadian Lousewort is rated USDA 4-8 and RHS H6 — Hardy throughout the UK and northern Europe.

Can canadian lousewort survive winter outside?

Plant it out within USDA 4-8 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 canadian lousewort below its minimum temperature?

It tolerates winter lows to about −20 to −15 °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.