It is a very large evergreen tree with a straight cylindrical bole, and sheds its lower branches easily. It is a moderate light-demander, but the seedlings and saplings will grow under high shade, and in India it is used for underplanting other species. For good growth it needs a moist, well-drained, deep, fertile soil. It has some resistance to frost. but seedlings are sometimes killed by it. Young seedlings are liable to be damaged by browsing. Michelia champaca is rather sensitive to fire, and severe fires may kill the trees outright. However, plantations will survive light annual fires. It coppices well, and fire·damaged trees will often shoot from the base. Sudden exposure to the sun may cause the crowns to die and numerous epicormic branches to be formed.
It grows in Nepal between 450 and 1500 m, and tends to favour areas of higher rainfall, such as east of the Arun River, and the Pokhara area. It is a characteristic species of the evergreen forest of the Bhabar Terai and the lower foothills of the Siwaliks in eastern Nepal, and of some of the moister types of Shorea robusta forest; it is also found in the Schima-Castanopsis zone, again usually on moister sites. Its western limit is near the Kali Gandaki River. It is not found in the Himalaya west of Nepal, though it occurs on the Western Ghats in peninsular India; In the east its range extends to Vietnam. It is often cultivated as an ornamental tree.
It flowers and produces viable seeds at a relatively early age. Although it seeds almost every year much of the seed is destroyed by birds and rodents. It sometimes comes in as an understorey to moist Shorea robusta forest.
The seed ripens between August and mid-November in different localities; this can be seen when the capsules begin to open and reveal the seeds. The fruit should be collected by climbing the trees, as the seeds in fallen fruits are usually attacked by insects. There are 14,000-17,000 seeds kg-1. The seed is extracted by keeping the capsules in the sun until they are nearly open, and then putting the seed in water and rubbing it together with coarse sand to remove the fleshy red or pink aril which surrounds it. This aril contains a powerful germination inhibitor, and if it is not removed the. seeds will not germinate (Robbins, 1988). Seeds which float in water are infertile and should be thrown away. Storage of the seed has been investigated by Robbins. He found that seed stored without removing the aril did not germinate. In seed with the aril removed, dried to 11 per cent moisture content, and stored in sealed polythene bags at 5°C, the original germination percentage of 86 dropped to 50 by three months and to nil by nine months. Seed stored in moist sand at 5°C retained its viability well for at least nine months. In India partially dried seed (21 per cent moisture content) stored in sealed containers at room temperature was all dead within two months (Bahuguna et al., 1987). In practice the seed if mixed with damp sand, wrapped in wire gauze to prevent rodent damage, and buried 90 cm deep, can be stored for about four months without losing much viability. This is the most practicable method where refrigeration is not possible.
Seed sown in September, or in March after storing in pits, will begin to germinate 4-5 weeks after sowing. Stored seed sown later in the year will not germinate until the following spring. Two months may be needed before most of the seed germinates. Plant percentages in Nepal nurseries of 60-70 have been recorded, but 20-30 per cent is more usual. As germination tends to be irregular and rather protracted the seed should be sown in beds or trays, rather than directly into polypots. As the seed germinates, the seedlings should be pricked out, when they are still in the cotyledon stage. Thus it may be necessary to prick out on several occasions from the same seed bed. Polypots 10 cm x 18 cm lay-flat should be used, with a good potting mixture containing 20-25 pet cent compost The seedlings should be shaded until the primary leaves appear.
Below about 1000 m if seed is sown soon after collection in September to November, and germinates quickly, plantable seedlings will be ready by the next monsoon. At or above 1500 m an extra year in the nursery will be needed. At intermediate altitudes there may be difficulties, especially with seed that does not germinate before March or April; this will usually produce plants too small for planting in the next monsoon, but which may be too large if kept another year. To some extent their growth may be controlled by spacing and root pruning, or reducing watering. In India stumps from two-year-old plants have given good results in plantations, except that each stump produces numerous shoots which have to be pruned.
Because of the dangers from the champ bug, in India it is usual to plant M. champaca in mixture with other species, or as an understorey to other fast-growing species, such as Chukrasia tabularis.
The most important pest of M. champaca is the champ bug, Urostylis punctigera (Hemiptera), which has caused considerable damage in plantations in the duars of Bengal and Assam, that is in the region of relatively low altitude at the foot of the Himalaya. There are no records of this insect having become a pest in Nepal, and it may not be a problem at the higher altitudes at which M. champaca is usually planted in this country. The nymphs and adult bugs suck the sap from the leaves and young shoots; in older trees they may kill the crowns and branches up to a diameter of about 7.5 cm, while one-year-old plants may be killed completely within two weeks. Infections may be controlled by spraying the early stage nymphs when they cluster on the young leaves and buds at the ends of the branches, and later stage nymphs when they have migrated to the bark of stems and branches.
Michelia champaca has generally survived well in trials, even at altitudes of 2000 m or more, though initial growth rates are sometimes slow; about 50 cm after two years on average. Data from some older trials in Parbat District, Mid-Western Development Region (R.K. Shrestha and Gautam, 1991) included 79 per cent survival and a mean height of 1.9 m at five years old, and 75 per cent survival and a mean height of 5 m at seven years old, both at an altitude of 1800 m, on a gentle to moderate slope. These rates are slower than those recorded from India where average rates of growth from sample plot data in West Bengal are 2.4 m in height at two years, and 8.0 m in height by 8.6 cm dbh at five years, while a mean annual increment of more than 18 m3 ha-1 at eight years old can be expected (Forestry Research Institute, 1975). This is perhaps due to the moister and less harsh climate of West Bengal compared with much of Nepal. Volume tables are included in E. R. Sharma and Pukkala (1990).
It is a fodder species, though of relatively minor importance, and fodder supplies come from the forest rather than farmers' land. The timber is valuable. The heartwood is a light yellowish to olive brown and is widely used for furniture, doors and windows, and general carpentry and construction. The timber at 12 per cent moisture content weighs 460-660 kg m-3, and has a calorific value of 21,300 kJ kg-1 (heartwood). It is easy to saw and polishes well but is not durable. In India the flowers are distilled to produce a perfume; they are also used in religious ceremonies. Various parts of the tree have medicinal uses.
It was at one time a popular species with the local people. both for community plantations and private plantings. especially in the east. and in the region around Pokhara. However. survival in plantations has not been good; in 1981 and 1982 plantations of the Community Forestry Development Project it was only 42 per cent (J.G. Campbell and Bhattarai. 1983). Results from private plantings have been better, 77 per cent in 1983 (Community Forestry Development Project. 1984). Michelia champaca is a demanding species and plantations should be confined to areas of good soil in rather moist localities. Given these conditions it could be a useful timber tree, though so far the fast growth rates obtained in India have not been reached here.