CLOVE
Syzygium aromaticum Merr. and L. M. Perry, family MyrtaceaeThe clove tree produces flower buds that when harvested and dried become the cloves of commerce, which are used primarily as food spices. Clove oil, distilled from the plant, is used in perfumes, medicines, artificial vanillin, dentifrices, and other ways.
Purseglove (1968*) stated that the annual worldwide consumption of cloves was as follows: Indonesia, 8,000 metric tons; India, 3,000; Malaya, 2,000; United States, 2,000; Europe and North Africa, 3,000; and other countries, 1,000 metric tons - about 42 million pounds. Rosengarten (1969*) stated that Tanzania produces three-fourths of the world output.
Plant:
The clove tree, although related to the eucalyptus and some other large trees, is relatively small, 12 to 20 feet or, rarely, to 40 feet tall. The stem is often forked with two or three main trunks. The paired leaves are 3 to 5 inches long, 1 to 1 l/2 inches wide, and highly aromatic.
The plants are usually grown from seed, then set about 30 feet apart in the grove.
Inflorescence:
The clove tree inflorescence is a terminal branching cyme of 3 to 20 hermaphrodite florets, the whole about 1 l/2 inches long. Each pale yellow floret consists of a cylindrical thick ovary, one-quarter inch long. Above the ovary are four fleshy ovate sepals, and above these are the four tiny petals, numerous slender white 3/8-inch filaments, and a slender central style. The flower opens early in the morning. The united petals separate from the base as a cap, similar to the grape blossom, which is pushed off by the extending stamens. In a few hours, all the anthers are open, and the stigma is receptive (Wit 1969). There are two flowering seasons a year, July to October and November to January. Few flowers develop into fruit. The fruit, called mother of cloves, contains one seed or rarely two seeds. The ovary and sepals constitute the specific part marketed as cloves (Purseglove 1968*, Ridley 1912*).
Pollination Requirements:
Purseglove (1968*) said that no fertile fruits were obtained from bagged flowers. He concluded that cross-pollination was necessary for seed production. Tidbury (1949) stated that no viable seeds have been produced from selfed flowers, indicating that the flowers require cross- pollination. He also concluded that, since vegetative propagation had never been accomplished, pollination from the breeding standpoint becomes important.
Pollinators:
Purseglove (1968*) stated that the flowers are visited and apparently cross-pollinated by bees. Ridley (1912*) merely stated that the fertilization was by some insect. Tidbury (1949) stated that the flowers are visited by bees.
Pollination Recommendations and Practices:
No attempt is made to utilize insect pollination in the production of clove planting seed. The figures by Purseglove (1968*) on tree spacing, tree yields, and total production of cloves would indicate that about 70,000 acres are involved, and reproduction of plants occurs at the rate of about 1,000 acres per year.
The need for sufficient pollinating insects to produce the small amount of seed required to plant 1,000 acres of cloves is probably not acute. There would be a definite need for insect pollinators if the production were concentrated in certain areas and maximum seed production desired. If such were the case, bees could be concentrated in the planting to perform the required pollination.
No known attempts have been made to use pollinating insects in clove seed production.
LITERATURE CITED:
TIDBURY, G. E.
1949. THE CLOVE TREE. 212 pp. Crosby Lockwood and Sons Ltd., London.WIT, F. 1969. THE CLOVE TREE. In Ferwerda, F. P., and Wit, F., eds., Outlines of Perennial Crop Breeding in the Tropics, pp. 163-174. H. Veenman and Zonen, N. V. Wageningen, The Netherlands.
