Cold hardiness & minimum temperature

Is Coreopsis 'Mercury Rising' (Coreopsis 'Mercury Rising')cold hardy? Hardiness zone & min temp

Also called Mercury Rising Tickseed, Big Bang Mercury Rising Coreopsis.

More about coreopsis 'mercury rising'

About Coreopsis 'Mercury Rising'

Coreopsis 'Mercury Rising' · also called Mercury Rising Tickseed, Big Bang Mercury Rising Coreopsis · flowering

Coreopsis 'Mercury Rising', part of the Big Bang Series, is a sterile perennial tickseed prized for its dark wine-red flowers borne on upright, branching stems from late spring through summer. Sterility extends the bloom period as energy is not diverted to seed production. Best in full sun and well-drained soil. Coreopsis is non-toxic to pets per the ASPCA.

Cold limit: USDA 4-9 · RHS H6 (-15-30°C)

Watch for — Crown rot in wet winters: Poorly drained soils over winter are the main threat. Improve drainage or mulch lightly around (not over) the crown.

What coreopsis 'mercury rising''s hardiness rating actually means

Yes — coreopsis 'mercury rising' is genuinely cold hardy. Rated RHS H6 and USDA 4-9, it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H6 means: Hardy throughout the UK and northern Europe. On the US scale that maps to USDA 4-9 — 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 about −20 to −15 °C. Coreopsis 'Mercury Rising' is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for coreopsis 'mercury rising' as it gets too cold:

It tolerates winter lows to about −20 to −15 °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 coreopsis 'mercury rising' go outside or overwinter — and where?

Plant it out within USDA 4-9 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 coreopsis 'mercury rising' can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H6 figure above.

Coreopsis 'Mercury Rising' hardiness — frequently asked questions

Is coreopsis 'mercury rising' cold hardy?

Yes — coreopsis 'mercury rising' is genuinely cold hardy. Rated RHS H6 and USDA 4-9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Coreopsis 'Mercury Rising' is hardy across USDA 4-9; 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 coreopsis 'mercury rising' can survive?

Minimum survivable temperature is roughly about −20 to −15 °C. Coreopsis 'Mercury Rising' is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is coreopsis 'mercury rising'?

Coreopsis 'Mercury Rising' is rated USDA 4-9 and RHS H6 — Hardy throughout the UK and northern Europe.

Can coreopsis 'mercury rising' survive winter outside?

Plant it out within USDA 4-9 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 coreopsis 'mercury rising' below its minimum temperature?

It tolerates winter lows to about −20 to −15 °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.