Cold hardiness & minimum temperature

Is Oxalis Triangularis 'Mijke' (Oxalis triangularis 'Mijke')cold hardy? Hardiness zone & min temp

Also called green shamrock, Mijke oxalis.

More about oxalis triangularis 'mijke'

About Oxalis Triangularis 'Mijke'

Oxalis triangularis 'Mijke' · also called green shamrock, Mijke oxalis · houseplant

Oxalis triangularis 'Mijke' is the bright-green form of the false shamrock, with the same triangular trifoliate leaves that fold down each evening and reopen by day. It grows from small bulbs, flushes quickly in good light, and naturally cycles through dormancy. Easy and rewarding, it brings nyctinastic leaf movement and dainty pale blooms to a windowsill.

Cold limit: USDA 8-11 (grown as a houseplant or summer container elsewhere) · RHS H2 (15-24°C)

What oxalis triangularis 'mijke''s hardiness rating actually means

Oxalis Triangularis 'Mijke' 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 8-11 (grown as a houseplant or summer container elsewhere) — 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. Oxalis Triangularis 'Mijke' shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for oxalis triangularis 'mijke' 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 oxalis triangularis 'mijke' go outside or overwinter — and where?

It can live outside year-round only in the mildest, most sheltered part of USDA 8-11 (grown as a houseplant or summer container elsewhere) 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 oxalis triangularis 'mijke' 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 oxalis triangularis 'mijke'

Oxalis Triangularis 'Mijke' 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.

Oxalis Triangularis 'Mijke' hardiness — frequently asked questions

Is oxalis triangularis 'mijke' cold hardy?

Oxalis Triangularis 'Mijke' 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 8-11 (grown as a houseplant or summer container elsewhere) (and sheltered UK gardens) oxalis triangularis 'mijke' can stay out; in colder areas it must be lifted, brought in, or treated as a frost-tender plant.

What is the minimum temperature oxalis triangularis 'mijke' can survive?

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

What hardiness zone is oxalis triangularis 'mijke'?

Oxalis Triangularis 'Mijke' is rated USDA 8-11 (grown as a houseplant or summer container elsewhere) and RHS H2 — Tender — survives a frost-free greenhouse or a very mild, sheltered spot.

Can oxalis triangularis 'mijke' survive winter outside?

It can live outside year-round only in the mildest, most sheltered part of USDA 8-11 (grown as a houseplant or summer container elsewhere) 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 oxalis triangularis 'mijke' 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.