Cold hardiness & minimum temperature

Is Threadleaf Coreopsis (Coreopsis verticillata)cold hardy? Hardiness zone & min temp

Also called Threadleaf Coreopsis, Whorled Tickseed, Zagreb Coreopsis.

More about threadleaf coreopsis

About Threadleaf Coreopsis

Coreopsis verticillata · also called Threadleaf Coreopsis, Whorled Tickseed · flowering

Threadleaf Coreopsis is one of the most garden-worthy native perennials, forming airy mounds of finely cut, needle-like foliage smothered in bright yellow or pink daisy flowers from early summer to early autumn. Native to open woodlands and clearings of the eastern US, it is exceptionally drought-tolerant, long-lived, and the parent of many popular cultivars including 'Moonbeam' and 'Zagreb'.

Cold limit: USDA 3-9 · RHS H7 (-30–38°C)

Watch for — Crown rot in wet conditions: Standing water or heavy, waterlogged soils — especially over winter — cause crown and root rot. Ensure excellent drainage; amend clay soils with grit. Short-lived in boggy conditions. Divide regularly to maintain vigour.

What threadleaf coreopsis's hardiness rating actually means

Yes — threadleaf coreopsis is genuinely cold hardy. Rated RHS H7 and USDA 3-9, 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 3-9 — 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. Threadleaf Coreopsis is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for threadleaf coreopsis 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 threadleaf coreopsis go outside or overwinter — and where?

Plant it out within USDA 3-9 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 threadleaf coreopsis can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

Threadleaf Coreopsis hardiness — frequently asked questions

Is threadleaf coreopsis cold hardy?

Yes — threadleaf coreopsis is genuinely cold hardy. Rated RHS H7 and USDA 3-9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Threadleaf Coreopsis is hardy across USDA 3-9; 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 threadleaf coreopsis can survive?

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

What hardiness zone is threadleaf coreopsis?

Threadleaf Coreopsis is rated USDA 3-9 and RHS H7 — Hardy in the severest European continental winters.

Can threadleaf coreopsis survive winter outside?

Plant it out within USDA 3-9 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 threadleaf coreopsis 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.