Cold hardiness & minimum temperature

Is Vietnamese Coriander (Persicaria odorata)cold hardy? Hardiness zone & min temp

Also called Vietnamese coriander, Vietnamese mint, rau ram, Cambodian mint, laksa leaf, Asian mint.

More about vietnamese coriander

About Vietnamese Coriander

Persicaria odorata · also called Vietnamese coriander, Vietnamese mint · herb

Vietnamese coriander (Persicaria odorata), or rau ram, is a heat-loving Southeast Asian culinary herb with a peppery, cilantro-like flavour that does not bolt in summer heat. Give it bright light, constantly moist soil and warmth. Not listed by the ASPCA, but related buckwheat-family plants are toxic, so verify with your vet.

Cold limit: USDA USDA zones 9-11 (frost-free); RHS hardiness H2, tolerating 1-5°C. Overwinter indoors or under glass elsewhere. (14-30°C (optimal); damaged below ~5°C and killed by frost)

Watch for — Frost / cold damage: Frost-tender and killed by freezing temperatures; growth slows and leaves blacken below about 5°C (40°F). Bring containers indoors or take cuttings before the first frost to overwinter.

What vietnamese coriander's hardiness rating actually means

Vietnamese Coriander 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 (frost-free); RHS hardiness H2, tolerating 1-5°C. Overwinter indoors or under glass 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. Vietnamese Coriander shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for vietnamese coriander 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 vietnamese coriander 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 (frost-free); RHS hardiness H2, tolerating 1-5°C. Overwinter indoors or under glass 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 vietnamese coriander 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 vietnamese coriander

Vietnamese Coriander 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.

Vietnamese Coriander hardiness — frequently asked questions

Is vietnamese coriander cold hardy?

Vietnamese Coriander 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 (frost-free); RHS hardiness H2, tolerating 1-5°C. Overwinter indoors or under glass elsewhere. (and sheltered UK gardens) vietnamese coriander can stay out; in colder areas it must be lifted, brought in, or treated as a frost-tender plant.

What is the minimum temperature vietnamese coriander can survive?

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

What hardiness zone is vietnamese coriander?

Vietnamese Coriander is rated USDA USDA zones 9-11 (frost-free); RHS hardiness H2, tolerating 1-5°C. Overwinter indoors or under glass elsewhere. and RHS H2 — Tender — survives a frost-free greenhouse or a very mild, sheltered spot.

Can vietnamese coriander survive winter outside?

It can live outside year-round only in the mildest, most sheltered part of USDA USDA zones 9-11 (frost-free); RHS hardiness H2, tolerating 1-5°C. Overwinter indoors or under glass 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 vietnamese coriander 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.