Cold hardiness & minimum temperature

Is Aeonium Simsii (Aeonium simsii)cold hardy? Hardiness zone & min temp

Also called Sim's aeonium, mat aeonium, flathead aeonium.

More about aeonium simsii

About Aeonium Simsii

Aeonium simsii · also called Sim's aeonium, mat aeonium · houseplant

Aeonium simsii is a compact, low-growing aeonium from the Canary Islands that forms flat, tight rosettes of glossy green leaves fringed with fine white ciliate hairs and faint red lines. Unlike its taller cousins it stays small and clumps into mats. It enjoys bright light, gritty soil and cool, dry winters. Treat as potentially harmful to pets.

Cold limit: USDA 9-11 (indoor in most US homes) · RHS H2 (10-24°C)

What aeonium simsii's hardiness rating actually means

Aeonium Simsii is half-hardy (RHS H2). 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 H2 means: Tender — survives a frost-free greenhouse or a very mild, sheltered spot. On the US scale that maps to USDA 9-11 (indoor in most US homes) — 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 1 to 5 °C — tolerates cold but no real frost. Aeonium Simsii shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for aeonium simsii as it gets too cold:

Down to roughly about 1 to 5 °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 aeonium simsii go outside or overwinter — and where?

It can live outside year-round only in the mildest, most sheltered part of USDA 9-11 (indoor in most US homes) 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 aeonium simsii can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H2 figure above.

Frost protection for borderline aeonium simsii

Aeonium Simsii 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.

Aeonium Simsii hardiness — frequently asked questions

Is aeonium simsii cold hardy?

Aeonium Simsii is half-hardy (RHS H2). 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 9-11 (indoor in most US homes) (and sheltered UK gardens) aeonium simsii can stay out; in colder areas it must be lifted, brought in, or treated as a frost-tender plant.

What is the minimum temperature aeonium simsii can survive?

Minimum survivable temperature is roughly about 1 to 5 °C — tolerates cold but no real frost. Aeonium Simsii shrugs off cold nights but a real, sustained freeze will kill it.

What hardiness zone is aeonium simsii?

Aeonium Simsii is rated USDA 9-11 (indoor in most US homes) and RHS H2 — Tender — survives a frost-free greenhouse or a very mild, sheltered spot.

Can aeonium simsii survive winter outside?

It can live outside year-round only in the mildest, most sheltered part of USDA 9-11 (indoor in most US homes) 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 aeonium simsii 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.