Cold hardiness & minimum temperature

Is Basil-Leaved Sun Rose (Halimium ocymoides)cold hardy? Hardiness zone & min temp

Also called Basil-Leaved Sun Rose, Portugese Sun Rose.

More about basil-leaved sun rose

About Basil-Leaved Sun Rose

Halimium ocymoides · also called Basil-Leaved Sun Rose, Portugese Sun Rose · flowering

Halimium ocymoides is a compact evergreen shrub in the Cistaceae family native to Portugal and western Spain, named for its small, basil-like dark green leaves with a whitish woolly underside. In late spring to early summer it produces a profusion of bright yellow flowers, each with a bold chocolate-purple basal spot on each petal, creating a striking two-toned display. It demands full sun and sharply drained, poor soil and is one of the most drought-tolerant species in the genus — an excellent choice for dry, Mediterranean-style or gravel gardens. No confirmed ASPCA safety data is available; it is conservatively classified as mildly-toxic for pets.

Cold limit: USDA 8-10 · RHS H4 (-8 to 38 °C)

Watch for — Crown rot in wet winters: This is the primary cause of plant loss in UK gardens. Sitting in cold, wet soil over winter causes rapid crown and root rot. Ensure impeccable drainage and consider planting on a slight mound or raised bed in rainfall-heavy areas.

What basil-leaved sun rose's hardiness rating actually means

Yes — basil-leaved sun rose is genuinely cold hardy. Rated RHS H4 and USDA 8-10, it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H4 means: Hardy in an average winter across much of the temperate world. On the US scale that maps to USDA 8-10 — 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 −10 to −5 °C. Basil-Leaved Sun Rose is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for basil-leaved sun rose as it gets too cold:

It tolerates winter lows to about −10 to −5 °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 basil-leaved sun rose go outside or overwinter — and where?

Plant it out within USDA 8-10 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 basil-leaved sun rose can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H4 figure above.

Basil-Leaved Sun Rose hardiness — frequently asked questions

Is basil-leaved sun rose cold hardy?

Yes — basil-leaved sun rose is genuinely cold hardy. Rated RHS H4 and USDA 8-10, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Basil-Leaved Sun Rose is hardy across USDA 8-10; 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 basil-leaved sun rose can survive?

Minimum survivable temperature is roughly about −10 to −5 °C. Basil-Leaved Sun Rose is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is basil-leaved sun rose?

Basil-Leaved Sun Rose is rated USDA 8-10 and RHS H4 — Hardy in an average winter across much of the temperate world.

Can basil-leaved sun rose survive winter outside?

Plant it out within USDA 8-10 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 basil-leaved sun rose below its minimum temperature?

It tolerates winter lows to about −10 to −5 °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.