Cold hardiness & minimum temperature

Is Amaryllis (Hippeastrum hybrids)cold hardy? Hardiness zone & min temp

Also called Amaryllis, Dutch amaryllis, Knight's star lily, Barbados lily, Fire lily.

More about amaryllis

About Amaryllis

Hippeastrum hybrids · also called Amaryllis, Dutch amaryllis · flowering

Amaryllis (Hippeastrum hybrids) is a tender bulb prized for huge trumpet flowers on tall leafless stalks, popular for winter forcing indoors. It wants bright light, warm rooms, and sparing watering until growth starts. The ASPCA lists it as toxic to cats and dogs, so keep bulbs and plants out of reach.

Cold limit: USDA USDA zones 9-11 outdoors; grown as an indoor pot/forced bulb in cooler climates. (15-24C (active growth); 10-13C for dormancy)

What amaryllis's hardiness rating actually means

Amaryllis 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 USDA zones 9-11 outdoors; grown as an indoor pot/forced bulb in cooler climates. — 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. Amaryllis shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for amaryllis 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 amaryllis go outside or overwinter — and where?

It can live outside year-round only in the mildest, most sheltered part of USDA USDA zones 9-11 outdoors; grown as an indoor pot/forced bulb in cooler climates. 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 amaryllis 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 amaryllis

Amaryllis 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.

Amaryllis hardiness — frequently asked questions

Is amaryllis cold hardy?

Amaryllis 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 USDA zones 9-11 outdoors; grown as an indoor pot/forced bulb in cooler climates. (and sheltered UK gardens) amaryllis can stay out; in colder areas it must be lifted, brought in, or treated as a frost-tender plant.

What is the minimum temperature amaryllis can survive?

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

What hardiness zone is amaryllis?

Amaryllis is rated USDA USDA zones 9-11 outdoors; grown as an indoor pot/forced bulb in cooler climates. and RHS H2 — Tender — survives a frost-free greenhouse or a very mild, sheltered spot.

Can amaryllis survive winter outside?

It can live outside year-round only in the mildest, most sheltered part of USDA USDA zones 9-11 outdoors; grown as an indoor pot/forced bulb in cooler climates. 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 amaryllis 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.