Cold hardiness & minimum temperature

Is Sticky Santolina (Santolina viscosa)cold hardy? Hardiness zone & min temp

Also called Sticky santolina, Sticky lavender cotton.

More about sticky santolina

About Sticky Santolina

Santolina viscosa · also called Sticky santolina, Sticky lavender cotton · herb

Santolina viscosa is a rare evergreen sub-shrub endemic to the gypsum and marly-gypsum scrublands of southeastern Spain, primarily in the provinces of Murcia and Almería, where it grows at altitudes up to 600 m. Its common name refers to its distinctly sticky, viscid stems and foliage — an unusual characteristic within the Santolina genus. Like its relatives it demands full sun and sharply drained, poor soils, and it is particularly adapted to gypsum substrates. It is seldom cultivated outside specialist Mediterranean plant collections. Santolina is not listed on the ASPCA database; treat as mildly toxic to pets based on its aromatic oil content.

Cold limit: USDA 8-10 · RHS H3 (-5°C to 40°C)

Watch for — Winter cold damage in northern gardens: This southeastern Spanish endemic is less frost-hardy than many Santolina species; in the UK grow against a warm south-facing wall or in a cold greenhouse in USDA zone 7 or colder regions.

What sticky santolina's hardiness rating actually means

Sticky Santolina is half-hardy (RHS H3). It survives a mild winter outdoors in a sheltered spot, but a hard frost kills it — so in colder zones it is lifted, potted, or grown as a tender plant. Its RHS rating of H3 means: Half-hardy — comes through mild UK winters outside but is killed by a hard freeze. 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 −5 to 1 °C — a light, short frost only. Sticky Santolina shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for sticky santolina as it gets too cold:

Down to roughly about −5 to 1 °C it copes, especially if dry and sheltered.
A sustained hard frost collapses the top growth; whether it returns depends on whether the roots, crown or tubers froze.
Wet cold is far more lethal than dry cold for this plant — soggy, frozen soil is the usual killer.

Can sticky santolina go outside or overwinter — and where?

It can live outside year-round only in the mildest, most sheltered part of USDA 8-10 or a frost-free UK microclimate.
In colder zones, grow it in a pot you can move under cover, or lift its tubers/roots and store them frost-free over winter.
A south-facing wall, free-draining soil and a dry winter position can push it a full zone hardier than the books suggest.

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 sticky santolina can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H3 figure above.

Frost protection for borderline sticky santolina

Sticky Santolina is right on a hardiness edge in many gardens, so if you are pushing it, these measures buy it the margin it needs:

Mulch the crown or root zone deeply with bark, straw or leaf-mould before the first hard frost.
Move container plants against a warm wall or into an unheated but frost-free porch or greenhouse.
Fleece the top growth on the coldest nights, and keep it on the dry side — dry roots survive cold far better than wet ones.
Lift dahlia-type tubers or tender crowns after the first light frost blackens the foliage and store them somewhere cool but frost-free.

Sticky Santolina hardiness — frequently asked questions

Is sticky santolina cold hardy?

Sticky Santolina is half-hardy (RHS H3). It survives a mild winter outdoors in a sheltered spot, but a hard frost kills it — so in colder zones it is lifted, potted, or grown as a tender plant. Borderline outdoors. In its mild end of USDA 8-10 (and sheltered UK gardens) sticky santolina can stay out; in colder areas it must be lifted, brought in, or treated as a frost-tender plant.

What is the minimum temperature sticky santolina can survive?

Minimum survivable temperature is roughly about −5 to 1 °C — a light, short frost only. Sticky Santolina shrugs off cold nights but a real, sustained freeze will kill it.

What hardiness zone is sticky santolina?

Sticky Santolina is rated USDA 8-10 and RHS H3 — Half-hardy — comes through mild UK winters outside but is killed by a hard freeze.

Can sticky santolina survive winter outside?

It can live outside year-round only in the mildest, most sheltered part of USDA 8-10 or a frost-free UK microclimate. In colder zones, grow it in a pot you can move under cover, or lift its tubers/roots and store them frost-free over winter. A south-facing wall, free-draining soil and a dry winter position can push it a full zone hardier than the books suggest.

How do I protect sticky santolina from frost?

Mulch the crown or root zone deeply with bark, straw or leaf-mould before the first hard frost. Move container plants against a warm wall or into an unheated but frost-free porch or greenhouse. Fleece the top growth on the coldest nights, and keep it on the dry side — dry roots survive cold far better than wet ones. Lift dahlia-type tubers or tender crowns after the first light frost blackens the foliage and store them somewhere cool but frost-free.