Cold hardiness & minimum temperature

Is Trailing globe amaranth (Gomphrena serrata)cold hardy? Hardiness zone & min temp

Also called Trailing globe amaranth, serrate globe amaranth, trailing gomphrena.

More about trailing globe amaranth

About Trailing globe amaranth

Gomphrena serrata · also called Trailing globe amaranth, serrate globe amaranth · flowering

A spreading, low-growing annual with a trailing or cascading habit, bearing small, magenta-pink clover-like flower-heads in great profusion. Gomphrena serrata is especially valued for containers, hanging baskets, and ground cover in hot, dry conditions. It blooms continuously from summer to frost with virtually no maintenance.

Cold limit: USDA 2–11 (grown as annual) · RHS H2 (18–38°C)

What trailing globe amaranth's hardiness rating actually means

Trailing globe amaranth 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 2–11 (grown as annual) — 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. Trailing globe amaranth shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for trailing globe amaranth 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 trailing globe amaranth go outside or overwinter — and where?

It can live outside year-round only in the mildest, most sheltered part of USDA 2–11 (grown as annual) 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 trailing globe amaranth 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 trailing globe amaranth

Trailing globe amaranth 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.

Trailing globe amaranth hardiness — frequently asked questions

Is trailing globe amaranth cold hardy?

Trailing globe amaranth 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 2–11 (grown as annual) (and sheltered UK gardens) trailing globe amaranth can stay out; in colder areas it must be lifted, brought in, or treated as a frost-tender plant.

What is the minimum temperature trailing globe amaranth can survive?

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

What hardiness zone is trailing globe amaranth?

Trailing globe amaranth is rated USDA 2–11 (grown as annual) and RHS H2 — Tender — survives a frost-free greenhouse or a very mild, sheltered spot.

Can trailing globe amaranth survive winter outside?

It can live outside year-round only in the mildest, most sheltered part of USDA 2–11 (grown as annual) 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 trailing globe amaranth 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.