How to grow Vietnamese Mint in New Zealand
Vietnamese mint (Persicaria odorata), also called rau răm, Vietnamese coriander or laksa leaf, is not a true mint but a peppery, coriander-flavoured herb that is essential in Vietnamese and Malaysian cooking. Unlike true coriander, it does not bolt in summer heat. It grows fast in warm, damp, part-shaded spots and strikes easily from cuttings, but it is frost tender, so most gardeners outside the north keep a potted piece under cover over winter.
📖 Our full guide: How to Grow Vietnamese Mint in New Zealand
At a glance
When to sow by region
| Region | When to sow | Regional note |
|---|---|---|
| Northland | September to December | |
| Auckland | September to December | |
| Waikato & Bay of Plenty | October to December | Plant from October, once the inland frosts are over in late September. Warm coastal Bay of Plenty gardens can start a few weeks earlier under cover. |
| Central North Island | November and December | |
| Wellington & Lower North Island | October to December | Plant Oct to Dec once the soil has warmed, in a sunny spot sheltered from the wind. |
| Nelson & Marlborough | October to December | Frost tender. Plant Oct to Dec and keep a potted piece under cover over winter in frosty inland gardens. |
| Canterbury | November and December | Frost tender. Plant after the frosts in mid October and keep a potted piece under cover over winter. |
| Otago & Southland | November and December | Frost tender. Plant after the last frost in late October and keep a potted piece under cover over winter. |
| Central Otago | November and December | Frost tender. Plant after the last frost in early November and keep a potted piece under cover over winter. |
Not to be confused with: Mint, which it is not related to, and Coriander, whose flavour it shares but which runs to seed quickly in summer. Vietnamese coriander, rau răm and laksa leaf are other names for this same plant.
Where to plant
This herb loves warmth, moisture and part shade. Grow it in rich soil that never dries out, such as a damp corner, the edge of a pond or a pot standing in a saucer of water. It is frost tender, so it does best in Northland and Auckland and needs a sheltered, frost-free spot or a pot that can be moved under cover further south.
- Northland and Auckland: plant from September; it grows year round in frost-free gardens.
- Waikato and the Bay of Plenty: plant from October, once the inland frosts are over in late September. Warm coastal Bay of Plenty gardens can start a few weeks earlier under cover.
- Wellington and Nelson: plant from October to December once the soil has warmed, in a sunny spot out of the wind.
- Central North Island, Canterbury, Otago and Southland: plant in November or December after the last frost.
How to plant
- Stand a few stems from a bought bunch in a glass of water on a windowsill; roots appear within a week or two.
- Plant the rooted stems about 5 cm apart in pots, or 30 cm apart in the garden, in moist, rich soil.
- Water in well and keep the soil moist.
Watering and feeding
Keep the soil constantly moist; it wilts quickly in dry soil. In pots, standing the pot in a saucer of water keeps the mix damp. Feed weekly with a liquid fertiliser while it is growing strongly.
Pruning and care through the year
- Cut it back regularly to the firmer stems to encourage fresh, leafy growth.
- Before the first frost, pot up a piece and keep it in a bright, frost-free place over winter.
- Growth slows in cool weather, so harvests are smaller in winter.
Harvesting
Pick leaves and stem tips as needed. Cutting with scissors back to the firmer stems encourages bushier growth. The leaves are best fresh; add them at the end of cooking or scatter them over salads, noodle dishes and laksa.
Growing in pots
A pot at least 30 cm wide and deep in a sunny or part-shaded spot is ideal, and makes it easy to bring the plant under cover for winter. Keep the mix wet; a saucer of water underneath helps.
Propagation
Stems root readily wherever they touch moist soil and within a week or two in a glass of water, so new plants are easy to make at any time in the warm months.
Varieties
- Vietnamese Mint (Persicaria odorata)
Companion planting
This herb likes the same damp, rich conditions as other water-loving herbs.
Good companions
- Watercress Both like constantly moist soil and part shade.
- Coriander Used together in Southeast Asian cooking, and coriander appreciates the same part shade in summer.
Pests and diseases
This herb has few pests. Drying out and frost are the usual causes of losses.
Pests to watch for
Diseases to watch for
- Rust Small orange or brown pustules under the leaves. Remove affected stems.
Common questions
Is Vietnamese mint a real mint?
No. It belongs to a different plant family. Its leaves taste peppery and coriander-like rather than minty.
Is Vietnamese mint the same as rau răm or Vietnamese coriander?
Yes. Vietnamese mint, Vietnamese coriander, rau răm and laksa leaf are all names for the same plant, Persicaria odorata. It is neither a true mint nor a true coriander.
Can I use Vietnamese mint instead of coriander?
Yes, in most Southeast Asian dishes. The flavour is similar but stronger and more peppery, so use a little less. Unlike coriander, it keeps growing through hot summers without bolting.
How do I grow Vietnamese mint from a supermarket bunch?
Stand a few stems in a glass of water on a windowsill. They root within a week or two and can then be planted out or potted up.
Will Vietnamese mint survive winter?
In frost-free northern gardens, yes, though it slows down. Elsewhere, frost kills it, so keep a potted piece in a bright, frost-free place over winter.
Why is my Vietnamese mint wilting?
It needs constantly moist soil. Water more often, mulch, or stand the pot in a saucer of water.
Sources we checked: Yates NZ: How to grow Vietnamese mint; Kings Plant Barn: Herbs grow well guide.