Fast growing Eucalyptus trees are planted in tree plantations in Asia, Australia, Europe and the United States for fuel wood, poles, timber, lumber, biomass, essential oil and are an ecellent source of nectar for honeybees. Native to Australia, Eucalyptus trees are grown both by small farmers for profit and subsistence and by large conglomerates for industrial wood supply. Certain species of eucalyptus yield valuable essential oils, whilst some also provide an excellent source of nectar for honeybees. An estimated 50 million hectares of eucalyptus have been planted worldwide.
Eucalyptus Tree Facts
- Eucalyptus is the world’s most widely planted hardwood species
- Eucalyptus is prized globally for excellence in paper and energy production
- Eucalyptus grows faster than other hardwood species
- Eucalyptus will grow on upland landscapes, reducing pressure on environmentally sensitive areas
- Eucalyptus grows commercially with similar inputs to Pine
- Eucalyptus produces feedstock for fiber and energy in short rotations
Botanical Features :
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 ‘eucalyptos’ 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 can be easily propagated from seeds, as well as, through vegetative propagation by cuttings (clonal propagation). On an average, there are about 642,000 viable seeds per kilogram of seed and chaff mix. Dry seeds at 5-8% moisture content, can be stored in air tight containers under refrigerated conditions (3-5 0C) for more than 10 years without losing its viability.
Under nursery conditions, seeds are sown on raised beds under shade. Addition of mycorrhiza innoculum to the nursery soils by adding soil from natural eucalyptus forest is highly beneficial for establishment and growth of the plants. No pre-sowing treatment is required. Rapid and complete germination is achieved under moist, warm (25 – 35 0C) conditions in presence of light. Seedlings are pricked out and transferred to polybags at the second leaf -pair stage i.e. about 6 weeks from sowing. Seedlings are planted out in the field when they reach a height of about 25 cm i.e. about 3-5 months after sowing. This should coincide with the onset of monsoon season.
Plants at nursery stage are highly susceptible to damping off and other fungal diseases, which can be limited by strict attention to hygiene, reducing watering and shade and allowing good ventilation.
Silvicultural Characteristics :
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:
- Altitude range : 0 – 1000 m above sea level.
- Mean annual rainfall : 500 – 3000 mm
- Rainfall regime : summer, winter, bimodial: uniform
- Dry season duration : 0 – 8 months
- Mean annual temperature : 10 – 27 degree C
- Mean maximum temperature of hottest month : 22 – 42 degree C
- Mean maximum temperature of coldest month : -2 – 19 degree C
- Absolute minimum temperature : > -80 degree C ( data for upper limit NA)
Soil and Physiography
- Soil texture : light, medium, heavy
- Soil drainage : Free, seasonally waterlogged
- Soil reaction : acidic, neutral
- Special soil tolerances : saline
- Soil types : alluvial soils, gravely soils, ferral soils, red soils, sandy soils
Commercial uses of Eucalyptus :
- Eucalyptus is one of the fastest growing trees and is an excellent timber for paper and pulp, particleboard and hardboard industries.
- It is also an excellent source of fuelwood and charcoal.
- Eucalyptus wood is also used for light and heavy construction, railway sleepers, bridges, piles, poles and mining timber.
- Indian Standards are available for use of E. tereticornis timber, after treatment, for door frames, window shutters, furniture, cabinet, tool handles, packing cases and crates.
- Leaf extracts of the species have pesticidal properties and can be promoted as a biopesticide.
- The leaves of the species are rich in essential oils, that have many medicinal uses. Eucalyptus globulus can be raised commercially for Eucalyptus oil.
- E. tereticornis is a major source of pollen in apiculture and produces a medium amber honey of distinctive flavour.
- The wood and bark of the tree have a tannin content of 6-12% and 3-15% respectively, though not used as a commercial source of tannin.
- Eucalyptus is a large ornamental tree suitable for parks and avenue plantations.
- The tree may be used as an agro-forestry species. Eucalyptus in combination with pineapple have given excellent results in China.
- The tree species can be effectively used for regeneration of denuded lands and prevention of soil erosions in drought -affected areas.