This article throws light upon the top four factors influencing selection of trees. The factors are: 1. Purpose of Growing 2. Climatic Factors 3. Soil Factors 4. Availability and Cost Factors.
Factor # 1. Purpose of Growing:
(a) Specimen tree:
Such trees are planted singly for their attractive shape, beautiful foliage, flowers or for drooping branches which reflect humbleness, for example : Araucaria cookii, Callistemon lanceolatus, Salix babylonica, Cassia fistula, Magnolia grandiflora, Plume-ria alba, P. acutifolia, Cassia nodosa, Ficus elastica var. Decora or Black Prince, etc.
(b) Shady trees:
Such trees have mostly round canopy or umbrella crown. Leaves are large and dense so that no or very little sun is allowed underneath them. Common trees are Azadirachta indica, Kigelia pinnata, Alstonia scholaris, Ficus religiosa, F. benghalensis, F. infectoria, F. benjamina, Mimuspos elengi, Pterospermum acerifolium, Morus sp., Eugenia jambolina, Mangifera indica, Melia azedarach, Milletia oualifolia, Pongamia pinnata, Swietenia mahagoni, Swietenia macrophylla, etc.
(c) Flowering trees:
These trees produce colourful flowers and are planted for their beautiful flowers e.g., Bauhinia variegata, B. blakeana, Callistemon lanceolatus, Cassia fistula, Cassia nodosa, Cassia siamea, Delonix regia, Erythrina variegata var. Orientalis, Jacaranda acutifolia, Plumeria alba, Plumeria acutifolia, Butea monosperma, Chorisia speciosa, Heterophragmu adenQphyllum, Spathodea campanulata, Thespesia populnea, Lagerstroemia speciosa, etc.
(d) Trees for avenue or road side:
Trees planted along-side avenues or roads are generally for shade or for flowers. Commonly planted trees are Cassia fistula, Grevillea robusta, Jacaranda acutifolia, Heterophragma adinophyllum, Ficus infectoria, Milletia oualfolia, Kigelia pinnata, Pterosperomum acerifolium, etc.
(e) Screening purpose:
When tall upright trees are planted very close to give an ultimate look of curtain or screen. Such trees are planted to hide some objects or sides. For example, Greuillea robusta, Eucalyptus sp., Poplar sp., Polyalthia longifolia, P. pendula, etc.
(f) For fragrant flowers:
For this purpose trees like Kanak Champa (Pterospermum acerifolium), Pagoda tree (Plumeria sp.), Bara Champa (Magnolia grandiflora), Swarn Champa (Michelia champaka), Molsari (Mimuspos elengi), Akas neem (Millingtonia hortensis), etc. are suitable.
(g) For checking air pollution:
Industries are the major source of pollution and hence in such areas deciduous trees or trees having thick shining leaves will be more successful e.g. Morus sp., Poplar hybrida, Plumeria acutifolia, Ficus infectoria, etc.
Factor # 2. Climatic Factors:
Selection of trees will depend upon prevailing climatic conditions of the locality and trees of other climatic conditions may or may not do well or later on decline. This depends upon adaptability of individual types. Trees of tropical climate like Delonix regia, Neonauclea purpura decline later on in subtropical climate. Similarly, trees of temperate climate do not grow well in tropical regions.
Factor # 3. Soil Factors:
In general trees are adaptable to varying soil conditions but specific trees excel in particular conditions. In alkaline and saline soils, the trees which can be grown successfully are: Casurina equistiefolia, Cassia fistula, Parkinsonia aculeata, etc.
Factor # 4. Availability and Cost Factors:
The selection of trees for general planting should be done which are easily available at low price; however, specimen trees may be exception to this. For example, pants of Araucaria sp. or Ficus elastica var. Decora or Black Prince are sold at exorbitant prices but still these are in demand due to their beauty and rarity.