Cold hardiness & minimum temperature

Is Wild Quinine (Parthenium integrifolium)cold hardy? Hardiness zone & min temp

Also called Wild quinine, American feverfew, Prairie dock.

More about wild quinine

About Wild Quinine

Parthenium integrifolium · also called Wild quinine, American feverfew · flowering

Wild quinine is a robust, long-lived prairie perennial native to the eastern and central United States, valued for its dense, flat-topped clusters of small white flowers that bloom for weeks from late spring through midsummer. It is exceptionally tough, tolerating heat, drought, and clay soils that defeat most ornamentals, making it an outstanding low-maintenance choice for naturalistic gardens and pollinator plantings. The most important care fact is patience — plants invest heavily in a deep taproot during their first two years and may flower little before then. Wild quinine is not listed as toxic to pets by the ASPCA; it is classified here as mildly-toxic out of abundance of caution as individual assessment is limited.

Cold limit: USDA 4-8 · RHS H7 (-29 to 38°C)

What wild quinine's hardiness rating actually means

Yes — wild quinine is genuinely cold hardy. Rated RHS H7 and USDA 4-8, 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 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 below about −20 °C. Wild Quinine is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for wild quinine 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 wild quinine 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 wild quinine can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

Wild Quinine hardiness — frequently asked questions

Is wild quinine cold hardy?

Yes — wild quinine is genuinely cold hardy. Rated RHS H7 and USDA 4-8, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Wild Quinine 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 wild quinine can survive?

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

What hardiness zone is wild quinine?

Wild Quinine is rated USDA 4-8 and RHS H7 — Hardy in the severest European continental winters.

Can wild quinine 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 wild quinine 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.