Cold hardiness & minimum temperature

Is Kitten Tails (Besseya bullii)cold hardy? Hardiness zone & min temp

Also called Kitten tails, Kittentails, Bull's besseya.

More about kitten tails

About Kitten Tails

Besseya bullii · also called Kitten tails, Kittentails · flowering

Besseya bullii is a rare, conservative perennial wildflower endemic to six Upper Midwestern US states — Wisconsin, Minnesota, Iowa, Illinois, Indiana, and Ohio — where it inhabits dry sand prairies, oak savannas, bluff edges, and gravelly hillsides. It produces a basal rosette of woolly leaves from which a single fluffy spike of yellowish-green flowers emerges in April through June, standing 20–40 cm tall. The species is state-threatened or endangered across its entire range and is extremely sensitive to habitat disturbance, relying on periodic fire management to keep competing vegetation in check. Besseya bullii is not listed by the ASPCA and its safety for pets is unconfirmed; it is classified here as mildly toxic out of caution.

Cold limit: USDA 3-5 · RHS H7 (-40 to 30 °C)

What kitten tails's hardiness rating actually means

Yes — kitten tails is genuinely cold hardy. Rated RHS H7 and USDA 3-5, 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 3-5 — 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. Kitten Tails is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for kitten tails 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 kitten tails go outside or overwinter — and where?

Plant it out within USDA 3-5 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 kitten tails can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

Kitten Tails hardiness — frequently asked questions

Is kitten tails cold hardy?

Yes — kitten tails is genuinely cold hardy. Rated RHS H7 and USDA 3-5, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Kitten Tails is hardy across USDA 3-5; 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 kitten tails can survive?

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

What hardiness zone is kitten tails?

Kitten Tails is rated USDA 3-5 and RHS H7 — Hardy in the severest European continental winters.

Can kitten tails survive winter outside?

Plant it out within USDA 3-5 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 kitten tails 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.