Vietnamese mint

''Persicaria odorata'', with common names Vietnamese coriander, rau răm, laksa leaf, Vietnamese cilantro, phak phai, praew leaf, hot mint and Cambodian mint, is an herb with aromatic leaves, used in Southeast Asian and Northeast Indian cooking. The smell and taste are very similar to (but milder than) that of cilantro/coriander leaf — not that of coriander powder, the plant’s ground seed — making the plant a useful alternative for some individuals’ palates.

Vietnamese coriander is not related to the mints, nor is it in the mint family Lamiaceae, but its general appearance, growth habit and fragrance are somewhat reminiscent of them. ''Persicaria'' is in the family Polygonaceae, collectively known as the “knotweeds”, as well as "smartweeds" or "pinkweeds".

Food uses

Primarily, the leaf is prominent within Vietnamese cuisine, where it is commonly eaten fresh in salads (including chicken salad), and in raw ''gỏi cuốn''. Additionally, it can be found in some soups such as ''canh chua'' and ''bún thang'', and in stews such as fish '' kho tộ''. It is also popularly eaten with '' trứng vịt lộn'' (fertilized duck egg).

However, in Malaysia, Singapore and Indonesia, the shredded leaf is an essential ingredient of the ever-popular ''laksa'' (spicy noodle soup), so much so that the leaf is commonly referred to as "laksa leaf" (''daun laksa''). In Malaysia, where people commonly refer to the leaves as ''daun kesum'', it is used in the dishes ''nasi kerabu'' and ''asam pedas''.

In the cuisine of Cambodia, where the leaf is known as ( km, ជីរក្រសាំងទំហំ) ''chi krasang tomhom'', it is used in soups, stews, salads, and the Cambodian summer rolls, ''naem'' (ណែម).

In Laos and certain parts of Thailand, the leaf is eaten with raw or stir fried ground beef, called ''larb'' or ''”laab”'' ( lo, ລາບ).

The leaves are locally known as phak phai in Manipur, northeastern India. The Khoibu community grinds the leaves with ghost peppers and a nut locally known as "bonra" to make a spicy side dish.

In Australia, the plant is being investigated as a source of essential oil (kesom oil).

Characteristics

The Vietnamese coriander is a perennial plant that grows best in subtropical to tropical zones, in warm and damp conditions. In optimal conditions, it can grow up to .

The stem is jointed at each leaf. The top side of the leaves are dark green (with chestnut-coloured centre markings, typical of many ''Persicaria''), while the leaves’ undersides are a burgundy-red. This foliage colouring (green upper half, red or purple undersides) is indicative of a plant having evolved in lower or indirect light; I.e. the forest floor, where sunlight may be minimal or fleeting. Another example are the prayer plants, in the family ''Marantaceae'', especially ''Goeppertia'' or ''Stromanthe''. In order to survive, the plants will use their leaves’ darker undersides to help reflect and maintain all absorbed sunlight on the leaf surfaces for optimal photosynthesis. If a plant has leaves that are entirely green, sunlight may pass through them more easily, but ultimately those species are likely to grow in more exposed locations.

In Asia, it can be found cultivated or growing in the wild. It can survive very well, as an outdoor perennial, in the Mediterranean regions of the world (coastal Western USA, Chile, South Africa, Western Australia and Southern Europe), as well as any equatorial nation, and anywhere where frosts or freezing conditions are not common. It prefers full sun and well-drained soil. For colder climate zones, they should be brought inside for the winter and treated as a house plant. For climate zones that have milder winters, they will survive outside, although their growth may slow down. It rarely flowers outside the tropics.

Components

Its oil contains aldehydes such as decanal (28%), and the alcohols dodecanol (44%) and decanol (11%). Sesquiterpenes such as α-humulene and β-caryophyllene comprise about 15% of its oil.Kesom Oil – a New Essential Oil for the International Flavour and Fragrance Industry ''in'
First Australian New Crops Conference 1996 – Volume 2

C-Methylated homoisoflavanones ( 3-(4'-methoxy-benzyl)-5,7-dihydroxy-6-methyl-8-methoxy-chroman-4-one, 3-(4'-methoxy-benzyl)-5,7-dihydroxy-6,8-dimethyl-chroman-4-one, 3-(4'-hydroxy-benzyl)-5,7-dihydroxy-6,8-dimethyl-chroman-4-one, 3-(4'-hydroxy-benzyl)-5,7-dihydroxy-6-methyl-8-methoxy-chroman-4-one and 3-(4'-hydroxy-benzyl)-5,7-dihydroxy-6-methyl-chroman-4-one) can be found in the rhizomes of ''P. odoratum''.

Traditional uses

No scientific studies have measured ''P. odoratas effects on libido. Traditionally, in Vietnam, the herb is believed to repress sexual urges. A saying in Vietnamese states, ''"rau răm, giá sống"'' ("Vietnamese coriander, raw bean sprouts"), which refers to the common belief that Vietnamese coriander reduces sexual desire, while bean sprouts have the opposite effect. Many Buddhist monks grow coriander in their private gardens and eat it frequently, believing it helps them remain celibate.Vietnamese Coriander (Persicaria odorata (Lour.) Soják) page
from Gernot Katzer's Spice Pages

Cultivation

North American sources state Persicaria odorata can be grown outside in frost free parts of USDA Zones 9-11 in moderately fertile soil which is poor or well-drained but will remain moist to wet. It can tolerate full sun if there are breezes and boggy moist soil. However, part shade is desirable and it can be used as groundcover under trees.
If winter temperatures drop below 7°C/45°F overwintering indoors is possible if humidity can be maintained. Northern European sources proscribe all but summer under glass as it is hardy to H1C (minimum 5-10°C) with West and South facing aspects preferable.
Persicaria odorata grows up to 6-18 inches tall and wide (15-45 cm) in US and UK sources state 1 metre height by 1.5 m spread are possible in 2 to 5 years.
Pests and diseases are not regarded as being problematic and it is even resistant to deer and rabbit.

Propagation

Propagate by seed in autumn or spring but flowering and seed harvests are rare in non tropical climes.
In summer, propagation via semi-ripe cuttings should be straightforward. Rooting cuttings in water is so easy that North American sources recommend against overwintering indoors where humidity cannot be maintained. Rather, source fresh bunches of rau răm in early spring cost effectively from Asian supermarkets. Remove the young leaves at the very top of the stems and any large leaves along the stems. Trim the bottom off stems to the first healthy internode and place in water until 1-2 cm roots appear below the lowest node and then plant in soil. Expect to harvest around two months later.

References

External links

How to grow Persicaria odorata

Vietnamese instructional video on Persicaria odorata cultivation and propagation

English language instructional video on Persicaria odorata cultivation and propagation

{{Taxonbar, from=Q2593236
odorata
Malay cuisine
Flora of China
Flora of Indo-China
Plants described in 1790
Herbs
Medicinal plants