Agroforestree Database

Local names:
 Amharic (shito bahir zaf), Arabic (kafur limuni), English (spotted gum,lemon-scented iron gum,lemon-scented gum,lemon-scented eucalypt,lemon gum), French (eucalyptus a odeur de citron), German (Zitronen- Eukalyptus), Luganda (kalintusi), Spanish (citriod

Eucalyptus citriodora is a large, handsome evergreen tree, 24-40 (max. 50) m in height; tall, straight trunk, 60-130 cm in diameter; open, graceful crown of drooping foliage; bark smooth, white, powdery, sometimes pink, red or blue-grey, on large trunks dark or grey and shaggy.

Juvenile leaves alternate, ovate to broadly lanceolate, sometimes setose, petiolate, sometimes peltate; adult leaves alternate, lanceolate to narrowly lanceolate, 8-16 x 0.5-2 cm, acuminate, strongly lemon scented when crushed; petiole 13-20 mm long.

Inflorescence terminal and compound or axillary and simple; umbels 3 flowers; flower buds white, clavate; operculum hemispherical, 3-4 x 4-5 mm, apiculate.

Fruit ovoid or urceolate, 7-15 x 7-11 mm, often warty, with 3-4 deeply induced valves; seeds few, irregularly elliptical relatively large, shiny, black, 4-5 mm long.

The genus Eucalyptus was described and named in 1788 by the French botanist l’Héritier. The flowers of the Eucalyptus species are protected by an operculum, hence the generic name, which comes from the Greek words ‘eu’ (well) and ‘calyptos’ (covered). The specific epithet means lemon-scented.

Ecology

E. citriodora grows naturally on rolling undulating plateaux, including dry ridges, in open forest and woodland, generally on poor soils, from 80 to 800 m altitude. The species can survive a severe dry season.

In its natural range, the species is restricted to the central and northern coast of Queensland, with the main occurrence between Mackay and Maryborough, where it extends from the coast to over 200 miles inland. It is also common on a limited area of the higher and drier country near Atherton. The climate is tropical to subtropical and frost free near the coast, or with light frost inland at the higher altitudes. The main rainfall season is summer.

Native range
Australia

Tree management

Plantations can be established at a regular spacing of 3-4 m, but a spacing of 3 x 2 m is also practised. A mature tree is able to compete with weeds, although when young, good weed control (usually a 1m strip along each planting line) is essential, and 4-5 weedings each year for 2 years may be necessary before site occupancy is achieved. Growth is usually rapid, and subsequent management depends on the purpose for which the trees are being grown. If grown for pulpwood, the trees may be harvested after 6-10 years. Plantations grown for saw logs will require thinning.

Seed storage behaviour is orthodox. Viability is lost within 3 years in hermetic storage at room temperature with 13 + or - 2% mc. Hermetic storage at 4-6% mc and subzero temperatures is recommended. There are 140 000-220 000 seeds/kg.

E. citriodora grows naturally on rolling undulating plateaux, including dry ridges, in open forest and woodland, generally on poor soils, from 80 to 800 m altitude. The species can survive a severe dry season.

In its natural range, the species is restricted to the central and northern coast of Queensland, with the main occurrence between Mackay and Maryborough, where it extends from the coast to over 200 miles inland. It is also common on a limited area of the higher and drier country near Atherton. The climate is tropical to subtropical and frost free near the coast, or with light frost inland at the higher altitudes. The main rainfall season is summer.

E. citriodora seeds freely and regenerates naturally from seed. It can be propagated easily from seed, which germinate in 4-20 days. Seedlings are best raised in trays filled with sterile, fine loamy sand. The trays should be kept in the shade for the 1st few days after sowing, but light can be gradually increased to 50% full sunlight. Seedlings can be transferred from planting tubes when they have 2-3 leaf pairs. Further growth requires sunlight. The seedlings are ready for planting out when they are 25-30 cm in height, usually after 3-4 months. About 2 weeks before planting into the field they should be hardened off by reducing watering and removing shade. Most planters raise seedlings in a nursery for transplanting later. Container-raised seeds have high survival rates and rapid early growth. In Thailand in the early 1980s, annual seedling production of E. citriodora was approximately 2 million.

Vegetative propagation is possible from branch cuttings, but these should be taken from trees less than 2 years old. Best results are obtained from cuttings containing a stem node and a segment of a leaf. Hormones such as indole-acetic acid, indole-butyric acid or nephthalene acid will improve propagation success.

E. citriodora is planted for reforestation.

Apiculture:  E. citriodora is a favourite of beekeepers because of the high quality and quantity of honey produced. Honey produced is light amber.

Fibre:  The tree is planted as one of the better eucalypts for producing pulp in low-altitude areas of tropical and subtropical regions.

Timber:  The wood density is 785-990 kg/cubic m at 12% mc. The wood is heavy, strong, tough and resistant to termites. The heartwood is light brown to grey-brown and sometimes waxy to the touch. The sapwood is whitish, pinkish or cream, usually 25-60 mm wide, but the width varies with growth rate. The grain is straight to interlocked, forming a ribbon stripe when quarter-sawn; a fiddleback pattern is sometimes evident. The timber is used for general construction, bridges, railway sleepers and ties, flooring, poles, sporting goods, agricultural implements and tool handles.

Medicine:  The oils are used with steam and other preparations as an inhalant to relieve colds and influenza symptoms. Because of the refreshing odour of the oil and its efficiency in killing bacteria, it also finds application as antiseptic.

Ornamental:  It is cultivated in Australia, Brazil and North Africa for beautification.

Intercropping:  Studies in Nigeria suggest that beans are incompatible with E. citriodora, but maize and sorghum may be compatible. Addition of fertilizer can offset to an extent the depressive effects of E. citriodora on crops.

Essential oil:  The commercially important eucalyptus oil distilled from the leaves of this and other Eucalyptus species has medicinal and industrial uses.