TREES AND WHY WE NEED VARIOUS TREES

WHY DO WE NEED VARIETY OF TREES

SPECIMEN TREES

The purpose of growing specimen trees is to provide shade, add intimacy to the landscape and design as well. Bara Champa (Mangolia grandiflora), Christmas Tree (Araucaria cookii), Bottle Brush (Callistemon lanceolatus) and Amaltas (Cassia fistula) are common specimen trees can be seen around.

FLOWERING TREES

Mexican Silk Cotton Tree (Chorisia speciose), Nili Gulmohar (Jacaranda acutifolia), Bottle Brush, India coral tree (Erythrina indica), Pegoda (Plumeria rubra), Pegoda (Plumeria alba) are most common example of Flowering trees. Flowering trees have a predominant feature of landscape. Flowering trees provide burst of fragrance, colorful flowers and beauty of blooms.

SHADY TREES

They have a great impact on landscaping as they can beautify our yards, freshens up the surroundings by improving air and water quality and reduce energy costs. Neem (Azadiractha indica), Pilkhan (Ficus infectoria), Devil’s tree (Alstonia scholaris), Molsari (Mimusops elengi), Kigelia pinnata, Ficus religiosa, Banyan Fig (Ficus benghalensis), Ficus lacor, Pterospermum acerifolium, Eugenia jambolana (Jamun), Mangifera indica (Mango), Milletia ovalifolia, Pongamia pinata, Sweitenia mahogoni, Sweitenia macrophylla etc are common examples of shady trees.

TREES FOR ROADSIDE AND AVENUES

Trees on roadside or avenue play an important role in moderating micro-climate and sequestering green house gases. Selection of tree species must be according to their tolerance for roadside conditions. Though exotic tree species give immense flowering but they fail to withstand the harsh conditions and fall off after certain age during monsoon. Selection of such trees should be according to the road size. Following tree should be considered for planting along road side and avenue: Cassia fistula, Grevillea robusta, Jacranda acutifolia, Heterophragma adenophyllum, Ficus Infectoria, Milletia ovalifolia, Kingelia pinnata, Pterospermum acerifolium, etc.

SCREENING PURPOSE

Use of screening trees is to create a beautiful natural screen. Main purpose of screening trees is to hide or modify some objects or sides, to block wind, dust, snow, to control noise and filter light. Trees used for screen should be tall and planted close to each other so that they can provide an ultimate look of curtain or screen. A row of such trees is a great alternative of fence in the narrow space between homes. Some commonly grown such trees are Grevillea robusta, Eucalyptus, Poplar, Polyalthia longifolia, Bentula pendula , etc.

TO CHECK AIR POLLUTION

These are used to reduce the effect of pollution caused by industries and vehicles. The trees having shining leaves like deciduous trees would be more effective in absorbing air pollutants. Some common examples are Neem (Azadirachta indica), Ailanthus excesla, Alstonia scholaris, Polyalthia longifolia, Poplar hybrid, Plumeria acutifolia, Ficus infectoria, Pongamia pinnata, Dalbergia sissoo (commonly known as Talli), Morus alba., etc.

THE KIND OF SOIL AND CLIMATE REQUIRED TO GROW VARIOUS TREES

Soil requirement varies from tree to tree, as particular tree species grow best in particular soil conditions. For example: Eucalyptus requires well drained sandy soil for its successful growth. Alkaline and saline soils are best for growth of Casuarina equisetifolia, Cassia fistula, Parkinsonia aculeata etc. Mangifera indica (Mango tree) grows well in red loamy soil. Saraca indica, Pongamia pinnata, Butea monosperma, Terminalia arjuna etc are grown in saline soils.

 Climate factors include light, temperature, relative humidity, air and rainfall. These factors have a great influence on growth and development of trees. Different trees species are adapted to different climate conditions; therefore trees for a specific site should be selected according to the prevailing conditions of that particular site. Trees of other climate conditions may or may not grow successfully. For example, trees from a temperature regions (Oak, walnut, Abies alba, Abies grandis, Abies procera, Juniperus sabina etc.) require moderate rainfall and cannot grow in tropical regions where rainfall is high. Banana tree, papaya tree and bougainvillea etc. are trees of tropical regions which require high amount of rainfall for their growth. Neonauclea purpurea and Delonix regia are trees from tropical climate that decline later on in subtropical climate. Therefore selection of trees must be made according to the prevailing climatic conditions.

METHODS OF PLANTING TREES

Propagation– Propagation of trees has following methods

1. Seeds (sexual): Raised nursery beds in mid February to mid mid march and July to august.
2. Propagated vegetatively (asexual) in mid June to mid July.
3. Transplant after 4-5 weeks in the polythene bags.

Preparation of Ground- Trees are tall and perennial plants and live for several years hence ground preparation should be done in such a way that it is worth to support the growth of the trees. According to landscape plan, pits should be dug of 60 x 60 x 60cm in size. 8-10kg well rotten farmyard manure should be mixed with soil to fulfil nutrient requirements. To control attacks of termites 5% chlorpyriphos @ 5 ml/ litre of water is mixed in soil. After refilling the pit, immediate watering is required to settle down the soil followed by planting of tree in the center of the pit. In the event of depressions taking place because of irrigation, more soil should be added to the pits to fill them up to the level of the land. The pits are then ready for planting trees. Ideal distance between tall and spreading trees  should be 35-40 feet. Medium size & Dwarf trees are to be 25-30 feet & 15-20 feet respectively.

Planting time- Planting of trees varies according to variety of trees and climatic conditions. In India, there are two seasons of planting – Monsoon (June- August) and Spring (Feb to March).

For planting evergreen fruit trees like citrus and mango, monsoon season is the best. If the trees are planted early in the rainy season, they soon establish themselves and grow vigorously due to high moisture in the air and low desiccation of plants. Deciduous trees may be planted during the dormant period without shock mostly in January- February. Care should be taken that planting is done before the growth starts, otherwise trees suffer severely and will be in poor condition to withstand the oncoming hot weather.

PLANTING SCHEME FOR ROADSIDE

Such scheme varies from road to road i.e. width of road and vehicular traffic. Plant must be appropriate to the ecology of the site and local area. For wider roads- tall trees, for narrow roads- dwarf tree species and for medium roads – medium sized trees are selected.

Tall shady trees with 20 to 30 meters wide belts are effective in reducing noise pollution caused by traffic on national highways. Following are some trees which should be planted on national highways-Ficus Infectoria, Azadirachtha indica, Terminalia arjuna, Kigelia pinnata, Millingtonia hortensis, Polyalthia longfolia, Eucalyptus, Mangifera indica, Sygizium cumini, Delbergia sissoo etc.

Inner roads of colonies and cities are planted with the colorful trees (7 to 15m belts) such as Acacia longifolia, Acacia dealbata, Acacia pyracantha, Bauhinia variegata, Bauhinia blakeana, Barringtonia racemose, bauhinia speciosa, Butea monosperma, Callistemon lanceolatus, Cassia fistula, Cassia nodosa, Cassia siamea (Senna Siamea), Delonix regia etc.

Trees for plantation can be selected based on type of pollution. Such trees inactive the air pollutants through chemical and biochemical processes. Trees with thick canopy having broad, hairy leaves and shiny waxy coating absorb dust particles and pollutants very effectively.

Shady trees planted on both sides of the road do not only provide shade but also provide coolness during hot weather. Common example of such trees are Ficus Infectoria, Mimusops elengi, Alstonia scholaris, Cedrella toona, Swietenia mahagoni, Swietenia macrophylla, Azadirachtha indica, Ficus religiosa, Mangifera indica and Polyalthia longifolia.

LANDSCAPE USES OF TREES

ENVIRONMENTAL

Provide shade and shelter, absorb pollutants and reduce wind speed

ECONOMIC

While costly to plant and maintain, a locality with plenty of trees will attract investment and higher house prices

AESTHETIC

Contrasting with the rigid outlines of buildings, creating an avenue, indicating the passing of the seasons.

• Form linkages between one building and another. Avenue planting links as entrance with a large building or in a town or city creates a network of trees lines trees.
• In urban areas, street trees, trees in public open space, retail parks and trees in private gardens form the urban forest.
• In rural areas, trees define boundaries of fields, are grown as specimens in fields, provide shelter for cattle and are integral part of their livelihood.