Azadirachta indica A Juss

Botanical features of neem

Geographical distribution:

The tree grows well in tropical and sub-tropical regions of the world. They are sensitive to frost and can be produced only in warmer regions of the world. Neem is a native of Assam and Burma of South Asia. National research council has reported its presence in various areas of Pakistan, Sri Lanka, Thailand, Malaysia, drier islands of Indonesia, northern parts of Yemen, Nigeria.

Distribution in India:

In India, it grows well in drier regions of many states like Karnataka, Andhra Pradesh, Tamil Nadu, Uttar Pradesh, Bihar, Orissa, Maharashtra and Rajasthan.

Nomenclature:

 Kingdom  Plantae  Family  Meliaceae
 Division  Magnoliophyta  Genus  Azadirachta
 Order  Sapindales  Species  Azadirachta indica A Juss.

Commonly known as neem, nimbi, vembu, nimb, kohumba.

Botanical description of Azadirachta indica

Habit and Habitat:

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It is a tall multipurpose tree. It shows deciduous habit during the month of Feb to March in dry regions. It is mainly grown as avenue tree. It grows well in temperature range from 45°C to 50°C and annual rainfall ranging from 400 to 1200 mm. It withstands adverse environmental conditions like drought, shallow and acidic conditions. It is noticed growing in a wide range of soil types. It establishes well in black cotton soils, alkaline soils, dry stony shallow soils and well-drained loamy soils.

Root System:

The root system consists of a strong taproot and well developed lateral roots.

Stem:

The trunk is almost straight with spreading branches. The tree grows up to 20m in height. Bark is dark grey, cracked in nature. It is moderately thick, furrowed longitudinally and obliquely, dark grey and reddish brown inside.

Leaf:

Leaves are glabrous imparipinnate alternate, exstipulate, 22.5 to 37.5 cm. They are medium to dark green leaflets (3-8 cm long). Leaflets are 7-17 in number. They are alternate, very shortly stalked, 6-7.5 cm long ovate-lanceolate, unequal at the base, the upper leaflet is longer than the lower one. Leaflet margin are dentate and pointed tips.

Floral Biology:

Flowering begins from March to June. The inflorescence bears 150-250 flowers. Individual flower is 5-6 mm long and 8-11 mm wide. Flowers are small, whitish or yellowish in colour. They occur in large numbers in drooping axes from the leaf axils up to 25 cm long. Usually the petals are 5 in number, imbricate oblong and 0.2 -0.4 cm in length. The flowers are bisexual. The honey scented flowers attract insects.

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Fruiting period is from June to August. Green fruits turn yellow on ripening. The fruits are greenish yellow coloured and ellipsoidal drupe (2cm) borne on axillary clusters normally one seeded. The fruit skin is thin and inner pulp is yellowish white fibrous material. The inner pulp is 0.3 -0.5 cm thick. The white hard inner shell of the fruit encloses the seed.

Crop improvement

Tree improvement program involves identification of superior quality trees with respect to seed yield and oil content. The collection of seeds and evaluation of elite characters of the trees are done for three consecutive years. The germplasm is maintenanced for further studies on variability and tree improvement programs.

Cultivation aspects

Germination:

Neem seeds lack dormancy, therefore no specific pre-treatment is required. Fresh seeds may be sown immediately after collection. Usually germination takes place within 15-30 days. The seeds retain viability only for 2-3 weeks.   

Establishment of seedlings, weeding and intercropping:

Fresh seeds are used for rising of seedlings in nursery. A thoroughly prepared potting mixture containing 1:2:1 of FYM: red soil and sand is used for filling the poly bags. The seedlings are watered throughout summer. These seedlings are used for planting in the next monsoon. A pit size of 45x45x45 cm in length, breadth and height is dug and tank silt / FYM is filled. The poly bagged seedlings along with a mound of potting mixture is planted in these pits. Neem can be used for block plantation or for bund planting depending on the requirement of the farmer. The initial growth is slow and a height of 6-12m can be expected in 20 years with a diameter of 25-30 cm. In block plantations, 6m x 6m spacing is followed. Silvicultural management of neem in a block plantation is very essential. After the third year of growth, the lower branches are removed to have a clean bole of 4-6 meters over 20 years of growth.

PropagationAI-img4

It can be propagated by seeds, seedlings, saplings root suckers or by tissue culture plants. The natural propagation of neem seeds is usually observed under the mother tree through dispersal by birds. Wedge grafting of genotypes is standardized for propagation.

Pest and diseases

The fungus Alternaria alternate causes wilting of leaves and spots on the leaves. Pseudomonas azadirachtae causes irregular leaf spots around the veins creating small holes later. Leaf spot disease is caused by a pathogen namely Cercospora sp., Laspeyresia koenigiana and Helopeltis antoni are the major pests of neem tree. Use of fungicides and pesticides helps in preventing the attack by fungi and pests.

Phyto-chemistry

The neem contains various forms of bitter principles; terpenes like liminoids (azadirachtin, meliantrol, salanin). The neem leaves contain quercetin (flavonoid) and nimbosterol (β- sitosterol) and liminoids (nimbin and its derivatives). Azadirachtin is an active principle with insecticidal property found in all parts of neem tree but high concentration is found in the kernels.

Uses

Medicine:

Neem is used to reduce insulin requirements without altering blood glucose levels (Hypoglycaemic activity). Neem treatment has shown to be involved in lowering of high cholesterol levels.

Wood:

It heals wounds and used in vomiting, skin diseases, cough, fever, worm infestation. It is more preferred in wooden panels, furniture, boat building, toys, and agricultural implements. It is a good firewood.

Leaves:

The neem leaves help in the treatment of neuromuscular pains. They are reported to remove toxins, purify blood and prevent damage caused by free radicals. The leaf extract is used to cure chicken pox, small pox and ulcers.

Fruits:

Fruits are antihemorrhodial and antihelmintic in nature.

Seeds:

The neem seeds are antihelmintic, antileprotic and antipoisonous. The seeds, leaves and dry neem cake are active ingredients in mosquito repellant coils.

Oil:

The neem oil is highly medicinal, anti-dermatonic and used in aromatherapy. It is one of the promising resources for biodiesel production.

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Neem oil and Biodiesel

Press Cake:

It is an excellent organic fertilizer and is rich in plant nutrients. The neem cake is active in increasing the growth, leafage, improves the general appearance of fruits and vegetables. It has antifungal properties. It increases productivity and soil fertility. It accelerates root development and overall plant growth.