Cold hardiness & minimum temperature

Is Globe candytuft (Iberis umbellata)cold hardy? Hardiness zone & min temp

Also called Globe candytuft, annual candytuft, garden candytuft.

More about globe candytuft

About Globe candytuft

Iberis umbellata · also called Globe candytuft, annual candytuft · flowering

Globe candytuft is a cheerful, fast-flowering hardy annual producing dense, rounded clusters of small flowers in shades of white, pink, lilac, and carmine. A member of the Brassicaceae family, it thrives in cool seasons and full sun with well-drained soil. Excellent for edging, containers, and cutting gardens; self-seeds modestly.

Cold limit: USDA 3-9 · RHS H6 (5–20°C)

Watch for — Short flowering season in heat: Iberis umbellata is a cool-season annual; flowering ceases and plants decline quickly once temperatures exceed 22°C. Make successive sowings every 3–4 weeks from early spring for extended colour. Autumn sowings provide spring blooms.

What globe candytuft's hardiness rating actually means

Yes — globe candytuft is genuinely cold hardy. Rated RHS H6 and USDA 3-9, 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 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 about −20 to −15 °C. Globe candytuft is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for globe candytuft 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 globe candytuft 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 globe candytuft can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H6 figure above.

Globe candytuft hardiness — frequently asked questions

Is globe candytuft cold hardy?

Yes — globe candytuft is genuinely cold hardy. Rated RHS H6 and USDA 3-9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Globe candytuft 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 globe candytuft can survive?

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

What hardiness zone is globe candytuft?

Globe candytuft is rated USDA 3-9 and RHS H6 — Hardy throughout the UK and northern Europe.

Can globe candytuft 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 globe candytuft 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.