Cold hardiness & minimum temperature

Is Prairie Dock (Silphium terebinthinaceum)cold hardy? Hardiness zone & min temp

Also called Prairie dock, Prairie rosinweed, Basal-leaved rosinweed.

More about prairie dock

About Prairie Dock

Silphium terebinthinaceum · also called Prairie dock, Prairie rosinweed · flowering

Silphium terebinthinaceum is a bold North American prairie native distinguished by enormous sandpaper-rough basal leaves (up to 60 cm / 24 in long) that remain near the ground while leafless, wiry flowering stems rise dramatically to 2-3 m (6-10 ft) in midsummer, bearing clusters of small yellow daisy flowers. Like all Silphium species it develops a deep taproot and is strikingly drought-tolerant but resents disturbance once established. The most important care fact is to site it where the impressive foliage can be appreciated and where its height will not shade shorter neighbours. Silphium species are not listed by the ASPCA as toxic to cats or dogs.

Cold limit: USDA 4-8 · RHS H7 (-34 to 38°C)

What prairie dock's hardiness rating actually means

Yes — prairie dock 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. Prairie Dock is built for winter — once established it takes hard frost and snow in its stride.

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

Prairie Dock hardiness — frequently asked questions

Is prairie dock cold hardy?

Yes — prairie dock 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. Prairie Dock 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 prairie dock can survive?

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

What hardiness zone is prairie dock?

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

Can prairie dock 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 prairie dock 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.