Cold hardiness & minimum temperature

Is Simpson's Juttadinteria (Juttadinteria simpsonii)cold hardy? Hardiness zone & min temp

Also called Simpson's Juttadinteria.

More about simpson's juttadinteria

About Simpson's Juttadinteria

Juttadinteria simpsonii · also called Simpson's Juttadinteria · houseplant

A critically endangered succulent mesemb endemic to Namibia, forming small clumps of pale grey-green to blue-green fleshy leaves. Produces white daisy-like flowers in autumn and winter. A winter grower requiring full sun, very sharp drainage, and a dry summer. Suitable for dedicated succulent collectors only.

Cold limit: USDA 9b–11 · RHS H3 (-5–32°C)

Watch for — Frost damage when wet: While the plant tolerates light frost when kept dry, wet soil in combination with frost causes cell damage and rot. Ensure the plant is kept completely dry if temperatures drop below 0°C.

What simpson's juttadinteria's hardiness rating actually means

Simpson's Juttadinteria 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 9b–11 — 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. Simpson's Juttadinteria shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for simpson's juttadinteria 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 simpson's juttadinteria go outside or overwinter — and where?

It can live outside year-round only in the mildest, most sheltered part of USDA 9b–11 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 simpson's juttadinteria 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 simpson's juttadinteria

Simpson's Juttadinteria 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.

Simpson's Juttadinteria hardiness — frequently asked questions

Is simpson's juttadinteria cold hardy?

Simpson's Juttadinteria 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 9b–11 (and sheltered UK gardens) simpson's juttadinteria can stay out; in colder areas it must be lifted, brought in, or treated as a frost-tender plant.

What is the minimum temperature simpson's juttadinteria can survive?

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

What hardiness zone is simpson's juttadinteria?

Simpson's Juttadinteria is rated USDA 9b–11 and RHS H3 — Half-hardy — comes through mild UK winters outside but is killed by a hard freeze.

Can simpson's juttadinteria survive winter outside?

It can live outside year-round only in the mildest, most sheltered part of USDA 9b–11 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 simpson's juttadinteria 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.