Trees are perennial, tall, with marked trunk and grow for several years, bear flowers and fruits. On this planet, trees are growing for the last 50 million years. In different biotic zones, different types of trees dominate which have developed through evolutionary process and ecological succession.
With the spread of human civilization and increase in population pressure, forests have been cleared for cereal production. Un-judicious felling of trees resulted into ecological imbalance, change in climate, desertification and deterioration of soil conditions.
Trees provide us fruits, shelter, shade, fuel wood, and timber wood for making furniture, ships, paper etc. Other economic products like rubber, broza, gum and resins are also obtained from trees. From medicinal viewpoint, parts of trees are also used to make medicines. The value of trees in terms of service given to the society is very high according to calculation done by T.M. Das.
Fifty year old tree weighing about 50 tonnes, would produce for the society in the next fifty years value worth of Rs. 1.57 m for different services, for instance value for oxygen—0.25 m, prevention of air pollution and cleaning of atmosphere—0.50 m; rain water and regulation of humidity in atmosphere—0.30 m; protection against soil erosion and silting of dams, reservoirs and rivers—0.25 m, shelter to birds—0.25 m and protein for cattle from tree leaves—0.02 m.
Trees play important role in improving total living of this planet. They maintain balance between oxygen and carbon dioxide which is essential for the life of fauna. Trees serve as natural air conditioner specially in hot and dry climates by increasing humidity around them through transpiration, lower down temperature and thus change microclimate of surroundings.
Trees regulate the rainfall and check the spread of desert. They are also the guardian of soil and check soil erosion by binding the soil particles with their roots. They improve fertility of soil by adding organic manure in the form of leaves every year. To check air pollution due to the gases, dust, smoke, planting of trees is highly advantageous.
Planting of trees alongside the roads has a long history and in early days large planting was done by Buddha Bhikshu. Emperor Ashoka and Sher Shah Suri were well known for planting trees along-side the roads. Mogul kings did not lag behind in planting of trees. Now-a-days with the increase in vehicular traffic, it has become much more compulsory to plant more trees.
Apart from all these virtues, trees have immense beauty from aesthetic viewpoint. They bring the change in skyline on account of variation in their height: shapes, foliage texture and flower colour. They are used in landscape plan for aesthetic and functional purposes.
Trees are used in garden as specimen, avenue plantation, wind breaks, and screening. A judicious planting of trees enhances the beauty of surroundings. As the trees are the framework of the garden, they should be easy growing, hardy and requiring little attention.
Trees are perennial and will live for several years. Since the preparation of ground is done just once so it is worthwhile to follow proper method of planting. According to the landscape plan, pits should be dug of 60 × 60 × 60 cm size.
Soil should be well mixed with 10-15 kg well rotten farmyard manure, 20-25 g of 5 per cent Chlorpyrphos @ 5 ml/1 of water which is essential to check the attack of termites. Refilling of pit should be done which is followed by immediate watering to settle down the soil. After settling down the soil, planting of trees is done in the centre of pit.
For mass plantation best planting time is rainy season. After 2-3 good showers planting should be done so that water does not become a limiting factor. Plants establish easily and grow luxuriantly. Planting can also be done in February-March depending upon the availability of water.