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Seed Production
Calliandra trees mature rapidly and usually flower and bear fruit within their first year. In Indonesia they set flowers year-round, but most seed is produced in the dry season (June- September).
To obtain seed for planting, the pods are collected when they turn brown. After I or 2 days of drying in the sun, they open to expose the seed inside. These shiny, black, teardrop-shaped seeds look like those of leucaena but are slightly larger (14,000 seeds per kg). They store reasonably well. (Seeds kept in a refrigerator at 4°C had retained full viability after 2.5 years.
However, seeds stored in cotton bags at room temperature decreased in viability from 75 to 60 percent in 1 year.) Nevertheless, there is usually no need to store seeds for long periods because calliandra sets fruits continuously.
The seeds germinate without treatment, but they germinate more quickly if boiling water is poured over them and they are allowed to cool and soak for 24 hours.
Direct Seeding
Plantations can be established by direct seeding. This is best done on prepared sites. Before seeding, for example, the rows should be free of weeds and the ground between should be roughly cultivated.
Indonesians place about five seeds in each planting spot. Successful germination depends on the subsequent rainfall pattern.
Direct seeding can be done from the air. In Central Java two trials to grow calliandra by sowing seeds from aircraft on land covered with Imperata grass were reportedly satisfactory provided the lands were plowed or burned beforehand; only partial success was obtained on untreated sites. In one trial the number of calliandra seedlings surviving after 7 years was 10.4 percent of the number sown. This was the highest percentage among the species being tested.
Nursery Practices
Seedlings are commonly produced by two methods. In the first, calliandra seeds are planted in plastic bags filled with topsoil. No fertilizer is added. Two seeds are sown in each bag. (If both develop, the smaller seedling is removed.) Seedlings are allowed to grow until they are about 20-50 cm tall with a root collar diameter of 0.5-1.0 cm. They are then ready for transplanting. Depending on the amount and type of vegetation in the area to be planted, some site preparation is necessary before planting seedlings. This may include clearing the complete area, or just clearing strips or spots.
The second method is to produce "stumps." Seeds are sown on the surface of a prepared nursery bed and lightly covered with sand. Seedlings are allowed to develop to a height of 75-100 cm, which usually takes about 4 months. They are then lifted and top- and root- pruned to about 30 and 20 cm, respectively. Any remaining leaves are usually stripped off.
Bundles of these stumps can be stored for up to 1 week in a moist, shady place before planting in the field. Stumps are useful for interplanting among other trees or for planting directly into weeds. On steep slopes or river banks stumps are also often used to ensure satisfactory establishment. They can also be prepared from the prolific natural regeneration that occurs beneath established trees.
So far, attempts at propagating calliandra using cuttings have failed.
Planting is usually done at the beginning of the rainy season, and spacing varies according to purpose. Firewood plantings normally use spacings of 1m x 1m or 1m x 2m.
On poor soils the seedlings react well to an initial treatment of fertilizer, especially phosphate.
The trees often need to be weeded during the first year, but the tree canopy closes after that and weeds seldom get out of hand.
Yields
Calliandra grows fast. In moderately good soils in Indonesia the
plants may be 3-5 m tall and
5 cm in diameter at stump height within 12
months. This is an optimum size for firewood for village cookstoves.
Although extensive data are not available, some results indicate that on reasonable soils the trees grow with heights averaging 2.5-3.5 m in 6-9 months. They can be harvested after the first year, yielding 5-20 m3 of fuelwood per hectare. The stumps coppice readily, their sprouts often becoming 3 m tall within 6 months. In eastern Java calliandra trees have been harvested annually for 20 years or more, providing 35-65 m3 of fuelwood per hectare per year.
Harvesting is best done at the end of the dry season because the onset of rains will produce quick sprouting. The cutting is done 20-50 cm above the ground to foster rapid resprouting.
The main problem in coppicing the plants this way is that "shock" may prevent the buds from sprouting. As noted, the weakened, newly coppiced stumps can get fungal infections that prevent sprouting.
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