Cold hardiness & minimum temperature

Is Spearmint 'Kentucky Colonel' (Mentha spicata 'Kentucky Colonel')cold hardy? Hardiness zone & min temp

Also called Kentucky Colonel mint, julep mint.

More about spearmint 'kentucky colonel'

About Spearmint 'Kentucky Colonel'

Mentha spicata 'Kentucky Colonel' · also called Kentucky Colonel mint, julep mint · herb

'Kentucky Colonel' is a large-leaved spearmint prized for mint juleps, with crinkled bright-green foliage and a sweet, intensely fragrant flavor. A vigorous, spreading perennial, it thrives in moist, rich soil and partial to full sun. Grow it in a pot or sunken bottomless container to contain its aggressive runners, and harvest leaves continuously through the growing season.

Cold limit: USDA 5-9 (hardy perennial; dies back in winter, returns from roots) · RHS H5 (15-24°C)

What spearmint 'kentucky colonel''s hardiness rating actually means

Yes — spearmint 'kentucky colonel' is genuinely cold hardy. Rated RHS H5 and USDA 5-9 (hardy perennial; dies back in winter, returns from roots), 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 5-9 (hardy perennial; dies back in winter, returns from roots) — 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. Spearmint 'Kentucky Colonel' is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for spearmint 'kentucky colonel' 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 spearmint 'kentucky colonel' go outside or overwinter — and where?

Plant it out within USDA 5-9 (hardy perennial; dies back in winter, returns from roots) 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 spearmint 'kentucky colonel' can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H5 figure above.

Spearmint 'Kentucky Colonel' hardiness — frequently asked questions

Is spearmint 'kentucky colonel' cold hardy?

Yes — spearmint 'kentucky colonel' is genuinely cold hardy. Rated RHS H5 and USDA 5-9 (hardy perennial; dies back in winter, returns from roots), it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Spearmint 'Kentucky Colonel' is hardy across USDA 5-9 (hardy perennial; dies back in winter, returns from roots); 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 spearmint 'kentucky colonel' can survive?

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

What hardiness zone is spearmint 'kentucky colonel'?

Spearmint 'Kentucky Colonel' is rated USDA 5-9 (hardy perennial; dies back in winter, returns from roots) and RHS H5 — Hardy in most of the UK and in cold winters.

Can spearmint 'kentucky colonel' survive winter outside?

Plant it out within USDA 5-9 (hardy perennial; dies back in winter, returns from roots) 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 spearmint 'kentucky colonel' 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.