Flacourtia rukam (PROSEA)
Flacourtia rukam Zoll. & Moritzi
- Protologue: Syst. Verz.: 33 (1846).
- Family: Flacourtiaceae
- Chromosome number: 2n= 22
- Flacourtia euphlebia Merr. (1914).
- Rukam (En)
- Prunier de Chine, prunier café (Fr)
- Indonesia: ganda rukem, rukam (Java), klang tatah kutang (Borneo)
- Malaysia: rukam manis, rukam gajah
- Philippines: amaiit (Tagalog), aganas (Bisaya), kalominga (Igorot)
- Laos: kén
- Thailand: takhop-thai (central), khrop-dong (Pattani)
- Vietnam: mung guân ru'ng.
Origin and geographic distribution
Rukam is widely distributed but scattered, both cultivated and wild, all over Malesia. It is apparently rare in the Moluccas and in New Guinea. It has been introduced in Indo-China, India and Thailand.
The ripe fruit can be eaten raw; it is rubbed between the palms of the hand because bruising the flesh eliminates astringency. It is also served in "rujak", a fruit salad with spicy sauce, pickled, or sweetened with sugar to make jam or confectionaries. The young leaves are eaten raw in side dishes. Immature fruit is used to prepare traditional medicine against diarrhoea and dysentery. The juice of the leaves is applied to inflamed eye-lids. In the Philippines a root decoction is taken by women after childbirth.
The wood is hard and strong and used to make household utensils such as pestles and furniture.
The dark purple-red fruit has white flesh. Analyses of the edible portion in the Philippines show the following composition per 100 g: water 77 g, protein 1.7 g, fat 1.3 g, carbohydrates 15 g, fibre 3.7 g, ash 0.8 g. The energy value is 345 kJ/100 g.
- Small tree, 5-15(-20) m tall; trunk and old branches usually crooked, furrowed, branched near the base; young stem and branches with strong, woody, simple or branched spines, up to 10 cm long, usually absent in clonally propagated trees.
- Leaves ovate-oblong or elliptic to oblong-lanceolate, (6.5-)10-15(-18) cm × (3-)4-7(-9) cm, glabrous or puberulous on midrib and nerves, often shiny dark green above, brownish-red and drooping when young, margins coarsely toothed; petiole 5-8 mm long.
- Inflorescences in few-flowered, short, axillary, finely pubescent racemes; pedicels 3-4 mm long; flowers greenish-yellow, usually unisexual; sepals 4, rarely 3-6, petals absent; male flowers with 8 orange or yellow-white fleshy disk-lobes and numerous stamens; female flowers usually without stamens, styles 4-6(-8), free, stigmas indistinctly bilobed.
- Fruit a globose, depressed-globose to obovate berry, 2-2.5 cm in diameter, light-green to pink or purplish-green to dark red with whitish, juicy, acid pulp, crowned by the 4-6(-8) small peg-like styles set in a circle. Seeds 4-7, flat.
Growth and development
The seed germinates readily and quickly. The young plants, if nursed well, bear much larger leaves than the full-grown tree, which is often sparsely foliated compared with Flacourtia inermis Roxb. Shoot growth occurs in more or less synchronous flushes. The length of the juvenile phase is not known. In Java the trees flower between June and August; the fruit ripens after about 14 weeks. Occasionally flowering occurs at other times of the year. Bisexual flowers are rare and male trees are needed for pollination. Insects are attracted by nectaries in the flower.
Other botanical information
Rukam varies much in the amount of pubescence and in shape and size of leaves. Big-leaved forms have been described as F. megaphylla Ridley and F. euphlebia Merr., narrow-leafed forms as F. peninsula Elmer. These species, originally described as distinct, are now considered to fall within the natural variation of F. rukam.
Rukam grows under humid tropical conditions up to 1500 m above sea level; it has been found growing wild at 2100 m elevation. Its natural habitat is primary or secondary forest, often along rivers, and the tree grows in the shade as well as in full sun. The tree appears to be fairly adaptable to a range of temperature, rainfall and soil conditions.
Rukam is usually grown from seed, but the tree produces root suckers which can be used for vegetative propagation, e.g. of spineless trees. Budding or grafting, also on other Flacourtia species, is possible. In Indonesia budding on F. inermis Roxb. is practised. The trees are spaced 8-12 m apart.
There is no information on husbandry and crop protection. Fruit flies and stem borers have been found on Flacourtia species and in Indonesia the leaf-eating caterpillars Pygaera restitura and Cupha erimanthis are found specifically on rukam.
There are no yield figures but the trees are generally quite prolific.
Rukam has received little attention and it is so often confused with other species, particularly F. inermis, that it is difficult to assess its position. The pattern of growth, flowering and fruiting through the year needs to be understood to strengthen the basis for selection of superior trees (high yield, good fruit quality, thornless trees). This could widen the perspectives for the crop, including production for processing.
- Kalshoven, L.G.E., Sody, H.J.V. & van Bemmel, A.C.V., 1951. De plagen van de cultuurgewassen in Indonesië. Deel 2. [Crop pests in Indonesia. Vol. 2.]. W. van Hoeve, Bandung. pp. 553-554, 641.
- Molesworth Allen, B., 1967. Malayan Fruits. Donald Moore Press, Singapore. pp. 59-62.
- Setiyati Sastrapradja (Editor), 1977. Buah-buahan [Fruits]. Lembaga Biologi Nasional LIPI, Bogor. pp. 110-111.
- Sleumer, H., 1954. Flacourtiaceae. In: van Steenis, C.G.G.J. (Editor): Flora Malesiana, Series 1. Vol. 5. pp. 69-77.
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