Eugenia caryophyllata Thunb.

Syzygium aromaticum is a small-medium sized evergreen tree, 8-30 m tall. Canopy medium sized, crown base low. Branches semi-erect and numerous. Leaves glabrous, with numerous oil glands on lower surface. Flowers small, in terminal cymose clusters, each peduncle bears 3-4 stalked flowers at the end. Sepals minute triangular projections. Fruit olive-shaped, 1-seeded, popularly referred to as ‘mother of clove’. Most of the plant’s parts are aromatic (leaves, flowers and bark). The brown, dried, unopened flower buds are called cloves, a name coming from the French "clou" meaning nail. Cloves are from a genus of 400-500 species of evergreen trees and shrubs. The generic name is derived from the Greek syzygios (paired), on account of the leaves and twigs that in several species grow at the same point. The specific epithet means aromatic.

The clove tree is monoecious, flowers are hermaphrodite and self-pollinating. The tree matures between 8-10 years after planting. Fruits mature approximately 9 months after flower initiation and are considered physiologically mature when the exocarp turns reddish-purple in colour. Flowering varies between areas, in India flowering is from February-May, in Zanzibar (Tanzania) July-September and October-January. Fruiting normally occurs 5-6 months after flowering.

Grown in loamy humus-rich soils, also in deep and loose laterite soils.

S. aromaticum is commonly found in woodland and rainforest.

Cloves have been used for thousands of years, trade between the "clove island" Ternate and China dates back 2500 years. Early references to cloves report that to approach the Chinese emperor, one had to have a few cloves in their mouths to sweeten their breath. The clove tree is endemic in the North Moluccas (Indonesia) and was of old cultivated on the islands of Ternate, Tidore, Bacan and the West coast of Halmahera. Natives planted a clove tree for each child born, they believed that the fate of the tree was linked to the fate of that child. The Dutch extended cultivation to several other islands in the Moluccas, keeping an effective monopoly in the clove trade, which guaranteed high profits to them. In 1816, the Dutch set a fire to destroy clove trees and raise prices. This sparked a bloody revolt which ended the Dutch monopoly, clove trees were introduced to other countries, the climate and politics of the area changed forever. Cloves brought in by Arab traders into Europe were very costly and played an important part in world exploration history. Seyyid Said ordered clove saplings from the Moluccas and encouraged extensive cultivation by local Zanzibar farmers. Wars were fought in Europe and with native islanders to secure rights to the profitable clove business. The heritage of 10 fortresses of Portuguese, Spanish, English and Dutch origin in Ternate, a small island 9 km diameter, is evidence of this scramble for influence. Around 1800 clove was introduced into India from Mauritius.

Clove is traditionally propagated by seeds extracted from ripe fruits and sown immediately. Seed viability is short, about 2 weeks, and should be sown fresh. Seeds germinate after 1-6 weeks, then transferred into polybags filled with potting mixture and allowed to grow. Planting is done in the monsoon at a spacing of 6 m either way. The plant is propagated from seeds sown during August-October. Ripe fruits are deskinned by soaking in water for 24 hours and rubbing with sand or ash, dehusked seeds should be sown immediately, as their viability deteriorates rapidly. Germination is generally poor and hardly exceeds 70% under the best conditions. Seeds are sown in rows, 12-15 cm apart and 2.5 cm below the soil, in raised nursery-beds, prepared under shade. Germination takes place in 4-5 weeks and seedlings are judiciously watered throughout the period in the nursery. Seedlings are transplanted when they attain a height of c. 25 cm.

Initially, clove trees need shade from banana plants or albizias. Clove trees live for more than 100 years, the oldest tree recorded is aged 375 years in Indonesia. Generally, it takes 20-30 years for clove to attain full bearing. First bearing is 8-10 years after planting, in Zanzibar (Tanzania) 4-6 years and in Indonesia 6-8 years. They should be grown in deep, fertile, moist but well-drained soil in full sun or partial shade. The plants thrive well with periodical summer irrigation. The tree fails to flower in very moist conditions. Manuring is required regularly for proper growth and flowering. Shallow trenches about 50-150 cm away from the tree are dug for manure application. About 15 kg of organic manure and 18 g phosphorous, 50 g potash is applied per plant in the initial years, mature trees (15 years) get 40-50 kg applications of organic manure and 250 g phosphorous, 300 g nitrogen, 750 g potash. Organic manure is applied with commencement of the monsoons whereas fertilizers are applied twice from May-June and September-October. Mulching of trees with fallen leaves and application of river-silt are also beneficial. Weeding should be done at regular intervals. Thinning is recommended to reduce branch overcrowding in trees. Dead and diseased shoots should be removed once or twice a year. Harvesting is carefully done by hand-picking the pink unopened, eugenol rich flower bud. Average tree yield per year is 4 kg but in some years yields of 8-10 kg are recorded. Clove yield is significantly related to tree canopy size which in turn depends on the type of clove, soil and tree age. The buds are then sun dried for 4-6 days i.e. until the floral stalk is dark brown.

Sumatra disease caused by the bacterium Pseudomonas solancearum causes mass decline in plantations due to dieback. The fungus Valsa eugeniae causes sudden death characterized by heavy leaf fall, this disease is linked with water stress and wilting associated with it can be arrested by watering. Seedling wilt is caused by fungi such as Colletotrichum spp., Rhizoctonia sp. and Trichoderma sp. Leaf rot is caused by Cylindrocladium guingiseptatum. Leaf spot, necrotic lesions, twig blight and flower bud shedding are caused by Colletotrichun gleosporiodes. The stem borer Sahyadrassus malabaricus is the most significant clove pest, the caterpillars bore into the main stem resulting in drastic drying of plant parts above the entry point, pouring a solution of 0.1% Quinalphos into the bore hole and plugging the opening checks further damage. Scales (Lecanium psidii) and mealy bugs (Planococcus sp., Pseudococcus sp.) damage tender shoots by sucking sap, usually well managed with 0.05% Monocrotophos or Dimethoate.

Seeds require a pretreatment of soaking in water for three days. Mature seeds have high vigour and better percentage of germination. There are about 1 100 seeds/kg.

Shade or shelter: This multi-stemmed tree offers cool shade. Intercropping: Clove can be interplanted in coconut farm, as many as 120 clove plants can be accommodated in 1 ha of coconut garden. Ornamental: This is a beautiful tree suitable for gardens. Other services: Jewish people smell cloves in the service that closes the Sabbath (Havdalah). Clove oil reportedly imparts spiritual uplifting, warming and stimulation benefits. In the Middle Ages people studded oranges with cloves as a protection against plague. They believed that this would ward off bad luck.

Food: The spice of commerce is the unopened flower bud on the terminal shoots of the twigs. Cloves are used in spice cookies and cakes. Much of the world crop is used in Indonesia for the extremely popular clove aromatized cigarettes, called "kreteks. India also consumes a considerable amount of clove. Essential oil: Clove oil is extracted by water distillation and mixes well with cinnamon, cedar, lavender, rose and bergamot. Essential oil content in good quality cloves may exceed 15%. The oil is dominated by eugenol (70-85%), eugenol acetate (15%) and beta-caryophyllene (5-12%). Cloves contain about 2% of the triterpene oleanolic acid. Poison: Clove oil is very potent and can cause gum irritation, it is advisable to dilute it with equal amounts of vegetable oil. For infants even milder dilution is required. Use should be avoided during pregnancy, or if with sensitive skin. Medicine: Taken internally (tea) for stomach upsets, chills and impotence. Flower buds chewed to freshen breath or ease toothache pain. Also applied externally (essential oil) for toothache, headache, cold, arthritis and rheumatism. Two little-known compounds in clove oil have shown "strong activity" against bacteria associated with plaque formation and gum disease. The oil is also useful for ulcers, bruises, burns, bronchitis, asthma, minor infections and colic. Sometimes used to ease nausea.