Introduction:

Ailanthus belongs to a small family of about 30 genera, comprising about 200 species of shrubs and trees. About 10 species of the genera are found in the country. It belongs to family Simaroubaceae.

Ailanthus (derived from ailanto, an Ambonese word probably meaning "tree of the gods" or "tree of heaven") is a genus of trees belonging to the family Simaroubaceae, in the order Sapindales (formerly Rutales or Geraniales). The genus is native from East Asia south to northern Australasia. They are fast-growing deciduous trees growing to 25-45 m tall, with spreading branches and large (40-100 cm) pinnate leaves with 15-41 long pointed leaflets, the terminal leaflet normally present, and the basal pairs of leaflets often lobed at their bases. The small yellow to greenish flowers are borne on branched panicles they turn reddish later in the year and eventually brown they stay on the tree for a long time; the male flowers have a strong odour. The odour tends to resemble the smell of strong cat urine or the spray of a male cat. Also, touching the leaves leaves an unpleasant smell on the hands. The fruit is a samara drawn out into a long wing with the seed in the middle. The wood is fine grained and satiny.

Botanical Features:

It is fast growing species with a small whitish trunk. Branches are thick and spreading with a massive spreading crown. The bark is greenish or grey and smooth in young trees while in old trees, the bark is rough having large conspicuous leaf scars. It has large branches starting right from trunk and perpendicular to the trunk which tend to curve upwards.

The leaves are shed during the cold season and the new leaves appear in March-April, 3-9 dm long, pinnate; leaflets 8-14 pairs, 10-15 cm long alternate or sub opposite, coarsely and irregularly serrate, oblique at base; petioles 5-8 cm long.

The flowers are small in size yellow in colour and arranged in panicles, appear in February – March in Central India and in the month of April in north India. The flowers appear in the large open clusters among the leaves; the male, female and bisexual flowers being intermingled on the same tree. Calyx lobes 1.5 x 1 mm, ovate triangular. Corolla petals 5, 4 mm long, ovate lanceolate reflexed, glabrous, Stamens 10 in the male flowers and 0 in the female flowers; filaments glabrous. Ovary 2-5 partite. Fruits samara, 4-7 x 1-1.2 cm lanceolate, acute at both ends, multiveined, twisted near base, reddish brown. The fruits are formed soon after flowering. The fruits ripen in May-June, just before the onset of monsoon.

Growth Characteristics:

Ailanthus excelsa Roxb. is a lofty deciduous tree, though it is widely distributed in the country, it grows in the semi-arid and semi moist regions. In its natural habitat the absolute maximum shade temperature varies from 450C to 47.50C and the absolute minimum from 00 to 12.50C. The mean maximum temperature in the month of May is generally the highest. The temperature varies from 300 to 42.50C. The mean daily minimum temperature in January, the coldest month of the year varies from 40 to 210C.

The mean annual rainfall ranges from 500 – 1900 mm, sometimes even up to 2500 mm. The mean relative humidity ranges from 40-80 per cent in January and from 60-90 per cent in July. It has been found to be a suitable species for planting in dry areas of Rajasthan with annual rainfall of about 400 mm. It avoids moist areas having high monsoon rainfall.

It can grow on a variety of soils but thrives best on porous sandy loams. It avoids clayey soils with poor drainage and waterlogged areas. It can grow even on shallow dry soils but the growth is poor. A. excelsa has given better performance as compared to other species in lateritic soils. The tree can be seen growing upto an elevation of 900 metres.

Silvicultural Characteristics:

A. excelsa is a strong light demander. The seedlings get easily suppressed by weeds as a result of shading. It is sensitive to drought and is moderately frost tender, being killed by frost in exposed situations. The prolonged droughts kill the seedlings, though the poles and trees are drought resistant. In places, where winters are damp as well as cold, seedlings do not easily grow. The tree coppices well and produces root suckers freely. The tree is very susceptible to waterlogging or excess of moisture in the soil. It is easily broken by wind due to the brittleness of the stem and branches. It can attain a height of 18 to 25 m and girth of 2.5 m and has a cylindrical bole.

Natural Regeneration

Its natural regeneration in the forest is usually not satisfactory. The seeds are very light and winged and are dispersed far wide by the wind. If the seeds fall on bare ground germination takes place early in the first rainy season after the fall of the seed, but the seedlings rarely survive due to the sensitiveness of the seedlings and their intolerance of heavy weed growth. A large proportion of seeds do not germinate and are destroyed. The seeds which are buried deep fail to germinate and seedlings in depression die due to poor drainage, weed competition and attack of pests.

• Natural regeneration through coppice and root suckers is adequate. Coppice shoots are thinned for better development.
• The seeds are available in May – June and natural regeneration comes up in July. Within one year the plant establishes itself.