Cold hardiness & minimum temperature

Is Hart's Pennyroyal (Mentha cervina)cold hardy? Hardiness zone & min temp

Also called Hart's Pennyroyal, Deer Pennyroyal, Cervina Mint.

More about hart's pennyroyal

About Hart's Pennyroyal

Mentha cervina · also called Hart's Pennyroyal, Deer Pennyroyal · herb

Hart's Pennyroyal is a slender, moisture-loving mint relative native to wet meadows and streamsides in southwestern Europe. Unlike true pennyroyal (Mentha pulegium), it is rarely grown as a culinary mint but is valued as a water garden edging plant, with delicate lilac flowers and a mild, spearmint-like fragrance. Hardy and vigorous in damp conditions.

Cold limit: USDA 6–10 · RHS H4 (−5–25°C)

What hart's pennyroyal's hardiness rating actually means

Yes — hart's pennyroyal is genuinely cold hardy. Rated RHS H4 and USDA 6–10, it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H4 means: Hardy in an average winter across much of the temperate world. On the US scale that maps to USDA 6–10 — 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 −10 to −5 °C. Hart's Pennyroyal is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for hart's pennyroyal as it gets too cold:

It tolerates winter lows to about −10 to −5 °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 hart's pennyroyal go outside or overwinter — and where?

Plant it out within USDA 6–10 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 hart's pennyroyal can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H4 figure above.

Hart's Pennyroyal hardiness — frequently asked questions

Is hart's pennyroyal cold hardy?

Yes — hart's pennyroyal is genuinely cold hardy. Rated RHS H4 and USDA 6–10, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Hart's Pennyroyal is hardy across USDA 6–10; 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 hart's pennyroyal can survive?

Minimum survivable temperature is roughly about −10 to −5 °C. Hart's Pennyroyal is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is hart's pennyroyal?

Hart's Pennyroyal is rated USDA 6–10 and RHS H4 — Hardy in an average winter across much of the temperate world.

Can hart's pennyroyal survive winter outside?

Plant it out within USDA 6–10 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 hart's pennyroyal below its minimum temperature?

It tolerates winter lows to about −10 to −5 °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.