Rhodomyrtus tomentosa (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Rhodomyrtus tomentosa (Aiton) Hassk.

Protologue: Flora 25(2): 35 (1842).

Family: Myrtaceae

Chromosome number: 2n= unknown

Synonyms

• Myrtus tomentosa Aiton (1789).

Vernacular names

• Downy myrtle, rose myrtle (En)
• Indonesia: kemunting (Malay), harendong sabrang (Sundanese)
• Malaysia: kemunting (Peninsular Malaysia), karamunting (Sabah, Sarawak)
• Cambodia: pûëch, sragan
• Thailand: thoh (Peninsular), phruat (Trat), phruat-kinluk (Prachin Buri)
• Vietnam: sim.

Origin and geographic distribution

Downy myrtle is growing wild and cultivated South-East Asia, India, Sri Lanka, and southern China. Occasionally it is grown outside this area.

Uses

Children compete with birds for the sweet, edible fruit. In some areas jam or jelly used to be made from the fruit, but it is only incidentally available in quantity. Old sources in Malaysia mention the use of the fruits as a cure for dysentery and diarrhoea. A decoction of the roots or leaves is drunk for diarrhoea and stomachache, and as a protective medicine after birth. In Indonesia, the crushed leaves are used to dress wounds. The wood-tar can serve as a black dye and has been used to blacken teeth and eyebrows. In Java and in Florida, where the downy myrtle is cultivated in gardens, the ornamental value of the shrub and its flowers is prized.

Properties

The whole fruit is edible. It contains sugars, vitamins and minerals. The purple pulp is juicy and sweet when fully ripe, otherwise slightly astringent.

Botany

• Evergreen shrub or small tree, up to 4 m tall; twigs, young leaves and inflorescences densely white or yellowish tomentose.
• Leaves elliptic to oblong-elliptic, 4.5-8 cm × 2.3-4 cm, opposite, coriaceous, with 3 conspicuous longitudinal veins, upper surface glossy, glabrous, lower surface white or yellowish tomentose with raised nerves; petiole 3-5 mm long.
• Flowers solitary or in 3-flowered dichasia in upper axils; peduncles up to 1 cm, pedicels 0.5-2.5 cm long; bracts elliptic, leaf-like, 6-12 mm long, bracteoles elliptic or ovate, 2-3 mm long, persistent; calyx campanulate, 5-7 mm long, tomentose, 5-10-ribbed, 5-lobed, persistent; petals 5, broadly obovate, 15-18 mm × 9-13 mm, red or pink; stamens numerous, 10-15 mm long, filaments pink; style 13-15 mm long; ovary 3(-4)-locular.
• Fruit an oblongoid berry, 10-15 mm × 8-10 mm, purplish-black, crowned by the calyx lobes, tomentose; wall 1 mm thick, pulp sweet.
• Seeds many in 6(-8) pseudo-locules, divided by thin false septa, compressed-reniform, 1.5 mm in diameter.

Two varieties are distinguished:

• var. tomentosa (synonym Myrtus canescens Lour.), occurring in South-East Asia, southern China and Indo-China; with white-tomentose leaves, lateral nerves 2-6 mm inside the margin, less than one-third of the distance from the leaf margin to the central nerve, apex not apiculate, veins not reticulate, pedicels 1-2.5 cm long;

• var. parviflora (Alston) A.J. Scott (synonym Rhodomyrtus parviflora Alston), occurring in India and Sri Lanka; with cream- or yellowish-tomentose leaves, lateral nerves 3-7 mm inside the margin, over one-third of the distance from the leaf margin to the central nerve, apex apiculate, veins reticulate, pedicels less than 1 cm long.

Fruit of cultivated plants is said to be far superior to that of wild plants. In Java, where downy myrtle is known only as a garden plant, it flowers in July-August and fruits in September-October. Fresh seed germinates within a week. The growth rhythm has not been studied.

Ecology

Downy myrtle thrives in open, often degraded sandy sites, along the shore and on river banks. Where it grows, other plants seem not to be able to compete with it, hence almost pure stands exist. It tolerates full sun and flooding. Var. tomentosa is generally found in such harsh environments, up to elevations of 300 m, rarely up to 1300 m. On the other hand, var. parviflora occurs in montane woodlands and grassland at altitudes of 1800-2700 m. Moist, somewhat acid soils are preferred; the plant is not well adapted to limestone soils.

Agronomy

In cultivation the shrub is normally propagated through cuttings. Plants raised in this way will bear fruit in about 2 years. Downy myrtle is easy to grow and no serious pests and diseases have been reported. The growth rate is moderate and if enhanced by heavy fertilization, flowering and fruiting suffer. There is no information on yield.

Prospects

Downy myrtle is a very showy shrub when in bloom and it would seem that the prospects for its use as an ornamental plant are better than for its role as a fruit crop.

Literature

• Burkill, I.H., 1966. Dictionary of the economic products of the Malay Peninsula. 2nd edition. Vol. 2. Ministry of Agriculture and Co-operatives, Kuala Lumpur. p. 1937.
• Corner, E.J.H., 1988. Wayside trees of Malaya. 3rd edition. Vol. 2. The Malayan Nature Society, Kuala Lumpur. pp. 596-597, plate 143.
• Scott, A.J., 1978. A revision of Rhodomyrtus (Myrtaceae). Kew Bulletin 33(2): 311-329.

Authors

A.M. Latiff