Eucalyptus belongs to the family Myrtaceae with about 300 species of the genus. The species is one of the fastest growing trees in the world and many species attain great heights. Eucalyptus amygdalin is the tallest known tree with specimens attaining a height of as much as 480 feet.
Basically, a native of Australia and Tasmania, Eucalyptus was introduced in India, by the British in 1843 in Nilgiri Hills as an experiment to find high yielding species for fuel and timber. It soon became a favoured species for the foresters/ commercial plantations, owing to its fast growth, non exacting, non- browseable and drought resistant nature and adaptability to a variety of agroclimatic conditions.
Eucalyptus is popularly known as gum tree, red iron tree, nilgiri or safeda. Many fast growing species suitable for commercial cultivation in India have been identified. Eucalyptus tereticornis and E. grandis are important commercial species with a clean straight bole and compact crown. Hybrid eucalyptus (combination to E. tereticornis and E. grandis /E. urophylla/ E. camaldulensis) has shown greater vigour and drought and insect resistant characters in the field conditions and are preferred planting stock for commercial plantations.
Eucalyptus is a fast growing, medium- sized to tall tree attaining 20-50m in height and upto 2m in diameter. The tree has a deep tap root system with mycorrhizal associations which increases its ability to draw nutrients and water. The tree has a smooth silvery white stem. The leaves are leathery in texture, hang obliquely or vertically and are studded with glands containing aromatic oil. Flowering takes place during July-August. Flowers in bud are covered with a cup- like membrane (whence the name of the genus, derived from the Greek 'eucalyptus' meaning- 'well covered'), which is thrown off as a lid when the flower expands. The fruiting occurs during September - October. The fruits are surrounded by a woody, cup-shaped receptacles and contain numerous minute seeds.
Eucalyptus is versatile, fast growing and strongly coppicing tree possessing a wide range of soil and climatic adaptability. E.tereticornis has the most extensive latitude range (9-380S) of any species in the genus. Basically a light demander, the growth of the species is very much reduced under shade. Eucalyptus is known for its drought hardiness, although annual rainfall of 800 mm is preferred. The species is also moderately salt tolerant and relatively fire resistant. Eucalyptus is generally regarded as frost sensitive, though in Uruguay, E. tereticornis has known to come up with reasonable success in regions where unseasonal frost is likely to occur. The species is known to suffer cholrosis and die-back due to the reduced iron absorption in alkaline soils. The species grows under a wide range of climatic/soil conditions from warm to hot, sub humid to humid and from good to degraded soils. The range of agro-climatic conditions of the species ( E. tereticornis) is given as under:
Soil and Physiography