Albizia procera, commonly known as white siris or karoi tree, is a species of large tree found natively in southeast Asia and India. It is most commonly found in open forests, but may also be found on the margins of rain forests and in monsoon and gallery forests. It is considered an invasive species in South Africa. Albizia procera is a fast-growing, semi-deciduous, nitrogen-fixing tree that has been widely introduced in tropical and subtropical regions of the world to be used as an ornamental, soil improver and fuelwood species. It has the potential to spread by seeds and by root suckers and also coppices readily after damage. This tree has become an invasive weed in disturbed and natural environments because of its aggressive growth, high drought tolerance and wide adaptation to different environmental and soil conditions. In South Africa, A. procera invades subtropical coastal bush and riverbanks and is a Category 1 plant on the Regulation 15 Declared Weeds and Invader Plants list, meaning the plant may not occur on any land other than in biological control reserves and land-owners are obliged to control it. In Cuba, Dominican Republic, Puerto Rico and the Virgin Islands, it is an aggressive colonizer of abandoned farmlands, pastures, roadsides and other highly disturbed sites.
The genus name Albizia honors the Florentine naturalist Filippo del Albizzi, while the species name is derived from the Latin word 'procerus', meaning 'very tall or high'.
A. procera is typically between 7 and 15 meters tall, although occasionally it reaches 30 meters in height. It is deciduous, going leafless in the dry season (August-September). The leaves are bi-pinnate, with 2-5 pairs of sub-opposite pinnae and a 10-30 centimeter rachis. The bark is smooth and light-colored, exfoliating to reveal a reddish color underneath. It produces sessile greenish-yellow flowers with long, threadlike white stamens, creating a puffball effect; these are borne on racemes 8-25 centimeters long. The flowers give way to rich red or reddish-brown flattened pods containing 6-12 small, greenish-brown seeds.
The risk of introduction of A. procera is very high across tropical and subtropical regions of the world. This species is widely promoted to be used as a soil improver in agroforestry systems, for wood and charcoal production and as an ornamental. Additionally, this species has the potential to escape from cultivation and become naturalized, especially in disturbed areas near cultivation.
A. procera is cultivated for timber or as fuel in Asia, Africa and the Americas. In India, the leaves are considered good fodder for animals such as cows, sheep, goats, and elephants. The wood makes good charcoal, and the resin is a good substitute for gum arabic. The leaves are said to be insecticidal, while the bark may be used to make fish poison.
Albizia procera is a useful tree for farm and amenity planting, light shade, firebreaks and for the rehabilitation of seasonally dry, eroded and degraded soils. In Cuba, it is used as a shade tree over coffee and in Himachal Pradesh, India, it has been tested successfully as an agroforestry species in an alley cropping system with rain-fed wheat (Triticum aestivum). In the Philippines, farmers conserve trees of A. procera in the landscape because they cast only a light shade, fix nitrogen and serve as a cash reserve as the trees are in demand by local carvers. In Bangladesh, A. procera is regarded as a soil improver and is used as a nurse tree in tea gardens, coffee and cocoa plantings.
Albizia procera has a large amount of non-durable, yellowish-white sapwood. The heartwood is hard and heavy, light or dark brown, with light and dark bands resembling walnut. It is straight-grained, splits readily, seasons well, works easily and is durable. The timber is strong, elastic, tough and hard. A. procera makes a good cabinet and furniture timber and is also suitable for general construction, agricultural implements, household products, poles, house posts, truck and bus bodies and packing cases. It is a suitable source material for paper pulp, giving satisfactory yields of bleached pulp. The fibres of A. procera are short and blending with a long-fibred pulp may be necessary to improve strength properties for some end uses. A. procera makes excellent charcoal and fuelwood. The high rate of biomass production, high proportion of biomass in stem and branches (91%) and observed vigorous coppicing after felling led to recommend the species for fuelwood production in Puerto Rico.
In India, the leaves of A. procera are considered good fodder for most ruminants (cattle, sheep, goats, elephants and deer) and the tree is lopped for fodder in several states. In Australia, it appears that early settlers regarded A. procera as a good fodder tree. According to Lowry and Seebeck (1997), the main natural feed source from A. procera when established at wide spacings in a silvopastoral system would be the fallen leaves during the period of low quality dry-season pasture. These leaves could be expected to have similar feed value to the leaves of Albizia lebbeck, but would be available much later in the dry season. According to Valkenburg (1997), mineral content of the leaves for N, K, Ca and Mg is adequate for animal production, but the Na and P contents are inadequate, suggesting that this species should not be used alone for fodder but in mixtures with other fodder species. The leaf has a high crude fibre and lignin content, indicating poor digestibility. In a study in West Africa, found that A. procera was inferior in feed value to A. lebbeck and A. saman.
The bark is a source of tannin, but yields are low. The pounded bark is used as a fish poison and the leaves are used as an insecticide in Nepal.