Cold hardiness & minimum temperature

Is Tasmanian Blue Gum (Eucalyptus globulus)cold hardy? Hardiness zone & min temp

Also called blue gum eucalyptus, Tasmanian blue gum, fever tree.

More about tasmanian blue gum

About Tasmanian Blue Gum

Eucalyptus globulus · also called blue gum eucalyptus, Tasmanian blue gum · herb

Tasmanian blue gum is a fast-growing evergreen tree with aromatic, eucalyptol-rich foliage and striking silvery-blue juvenile leaves that mature to long sickle shapes. Often grown for cut foliage, screening, or as a container plant pruned for its round young leaves. It needs full sun, sharp drainage, and protection from hard frost, and can reach enormous size if left unpruned in the ground.

Cold limit: USDA 9-11 (frost-tender young trees; mature plants tolerate brief light frost) · RHS H3 (10-30°C)

Watch for — Frost damage: Young trees are frost-tender; foliage blackens and dies back in hard freezes. Protect or overwinter container plants under cover.

What tasmanian blue gum's hardiness rating actually means

Tasmanian Blue Gum 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 9-11 (frost-tender young trees; mature plants tolerate brief light frost) — 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. Tasmanian Blue Gum shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for tasmanian blue gum 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 tasmanian blue gum go outside or overwinter — and where?

It can live outside year-round only in the mildest, most sheltered part of USDA 9-11 (frost-tender young trees; mature plants tolerate brief light frost) 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 tasmanian blue gum 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 tasmanian blue gum

Tasmanian Blue Gum 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.

Tasmanian Blue Gum hardiness — frequently asked questions

Is tasmanian blue gum cold hardy?

Tasmanian Blue Gum 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 9-11 (frost-tender young trees; mature plants tolerate brief light frost) (and sheltered UK gardens) tasmanian blue gum can stay out; in colder areas it must be lifted, brought in, or treated as a frost-tender plant.

What is the minimum temperature tasmanian blue gum can survive?

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

What hardiness zone is tasmanian blue gum?

Tasmanian Blue Gum is rated USDA 9-11 (frost-tender young trees; mature plants tolerate brief light frost) and RHS H3 — Half-hardy — comes through mild UK winters outside but is killed by a hard freeze.

Can tasmanian blue gum survive winter outside?

It can live outside year-round only in the mildest, most sheltered part of USDA 9-11 (frost-tender young trees; mature plants tolerate brief light frost) 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 tasmanian blue gum 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.