Cold hardiness & minimum temperature

Is Green Cotton Lavender (Santolina rosmarinifolia)cold hardy? Hardiness zone & min temp

Also called Green cotton lavender, Green santolina, Holy flax, Rosemary-leaved lavender cotton.

More about green cotton lavender

About Green Cotton Lavender

Santolina rosmarinifolia · also called Green cotton lavender, Green santolina · herb

Santolina rosmarinifolia is a compact, evergreen sub-shrub native to the Iberian Peninsula and northwestern Africa, thriving in hot, sunny, and sharply drained Mediterranean conditions. Its fine, needle-like, bright green aromatic foliage is distinctive within the genus, and it bears clusters of bright yellow button flowers in summer. The single most important care rule is excellent drainage: this plant will rot quickly in wet or waterlogged soil, especially over winter. Santolina is not listed on the ASPCA toxic or non-toxic plant database; as its aromatic oils can cause mild GI upset and contact dermatitis in sensitive individuals, treat it as mildly toxic around pets.

Cold limit: USDA 6-9 · RHS H5 (-15°C to 35°C)

Watch for — Root and crown rot: The most frequent killer: caused by waterlogged or poorly drained soil, especially in winter. Ensure the planting site has fast drainage and avoid mulching directly against the woody base.

What green cotton lavender's hardiness rating actually means

Yes — green cotton lavender is genuinely cold hardy. Rated RHS H5 and USDA 6-9, it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H5 means: Hardy in most of the UK and in cold winters. On the US scale that maps to USDA 6-9 — 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 −15 to −10 °C. Green Cotton Lavender is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for green cotton lavender as it gets too cold:

It tolerates winter lows to about −15 to −10 °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 green cotton lavender go outside or overwinter — and where?

Plant it out within USDA 6-9 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 green cotton lavender can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H5 figure above.

Green Cotton Lavender hardiness — frequently asked questions

Is green cotton lavender cold hardy?

Yes — green cotton lavender is genuinely cold hardy. Rated RHS H5 and USDA 6-9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Green Cotton Lavender is hardy across USDA 6-9; 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 green cotton lavender can survive?

Minimum survivable temperature is roughly about −15 to −10 °C. Green Cotton Lavender is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is green cotton lavender?

Green Cotton Lavender is rated USDA 6-9 and RHS H5 — Hardy in most of the UK and in cold winters.

Can green cotton lavender survive winter outside?

Plant it out within USDA 6-9 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 green cotton lavender below its minimum temperature?

It tolerates winter lows to about −15 to −10 °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.