Albizia lebbeck
(Indian siris)

Albizia lebbeck is a perennial, deciduous tree, native to Asia and introduced to tropical regions across the world as a shelter tree for cash crops, for erosion control, as a forage crop and as a source of hardwood. The species can tolerate a wide range of climates and soil types. It reproduces by seed or vegetatively by cuttings or coppicing. It has a range of invasive traits, which include high seed production, a high growth rate and nitrogen fixation, that allow it to invade disturbed areas and natural forests.

It is naturalized in many parts of the tropics including the Caribbean, Central America and South America; in some places it has also become invasive. For example, in Puerto Rico, it appears on a government invasive species list and is a category 2 invasive species in the Bahamas. The species is reportedly one of the 100 most serious invasive species, and a transformer species, in Cuba. In Florida, the species has been listed as a category 1 invasive species (most serious concern) since 1999.

It is also invasive in parts of Africa. In South Africa, A. lebbeck invades coastal bush and riverbanks, displacing native plants, and is a category 1 weed under the Conservation of Agricultural Resources Act, 1983. It is cultivated on Pacific Islands and sometimes naturalized and invasive along roadsides and in forest patches. For example, on Chuuk Island in the Federated States of Micronesia it is classed as invasive or potentially invasive and is monitored for spread, potentially requiring control.

Although it is native to Australia, it is spreading southward and becoming more common in southeast Queensland where it is now regarded as an environmental weed by some local authorities. It is also regarded as an environmental weed in some parts of north and northwest Western Australia.

The native distribution range of A. lebbeck is obscure due to its extensive cultivation. This species is probably indigenous to the Indian subcontinent and to those areas of South East Asia with a marked dry season, such as northeastern Thailand, parts of Malaysia and in the eastern islands of Indonesia (Little, 1983; `t Mannetje and Jones, 1992; Lowry et al., 1994). There are also natural populations in Australia occurring in the Kimberley region of Western Australia, the extreme north of the Northern Territory and far northern Queensland (i.e. the Cook pastoral district) (Doran and Turnbull, 1997; Weeds of Australia, 2016). In India it occurs throughout most regions, except in Jammu and Kashmir, Himachal Pradesh and Sikkim (India Biodiversity Portal, 2016).

Naturalized populations of A. lebbeck can be found in Africa, tropical South America, southern USA (California, Florida and Texas), the Caribbean and on some islands in the Indian and Pacific Ocean (Orwa et al., 2009; Acevedo-Rodríguez and Strong, 2012; ILDIS, 2016; PIER, 2016; PROTA, 2016; USDA-ARS, 2016).

A. lebbeck is actively promoted, particularly in relation to agroforestry where it is regarded as having potential for use in silvopastoral systems in dry and semi-arid regions (Lowry et al., 1989). This interest stems from its apparent ability to improve pasture production and quality, in addition to providing a food supplement in the form of the leaves, flowers and pods (Lowry et al., 1989). It has naturalized or become invasive in a number of locations and its future introduction to other sites has the potential to increase the number of locations where it is invasive.

A. lebbeck can be found growing in deciduous and semi-deciduous monsoon forests, rain forests and humid forests, but it is also adapted to dry forests and semi-arid habitats in tropical and subtropical regions (Cook et al., 2005; Orwa et al., 2009). Within its native range, A. lebbeck is often found on riverbanks and in savannas, forests and bushy areas (PIER, 2016). In its Australian range, A. lebbeck is a dominant species in semi-evergreen vine forests (monsoon forest) in areas with a mean annual rainfall of 1300-1500 mm and a very dry winter but is known to naturalize in coastal forests, savanna woodlands and riparian areas (Beadle, 1981; Hocking, 1993; Lowry et al., 1994; Parrotta, 2010; Ecocrop, 2016; Weeds of Australia, 2016; Purdue University, 2017). It is also in semi-deciduous microphyll vine thickets on scree slopes of quartz sandstone mountains (Miles et al., 1975), with a closed canopy of emergent trees 9-15 m tall. On lateritic plateaux, A. lebbeck grows with Hakea arborescens and Grevillea mimosoides in the shrub layer beneath low woodland and low open-forest. In India, it is found in tropical evergreen, semi-evergreen and deciduous forests in areas with a mean rainfall of 600 to 2500 mm (Troup and Joshi, 1983).

Genetics

The chromosome number reported for A. lebbeck is 2n = 26 (`t Mannetje and Jones, 1992).

Variation in height and diameter growth, branch number, biomass and chemical contents of seed and foliage were observed among twelve provenances of A. lebbeck collected throughout India (Kumar and Toky, 1994; Toky et al., 1996). Provenances from northwestern and central India, in general, were superior to those from south India. Apart from these reports, there is little information on its genetic variability and there are apparently no other programmes systematically screening provenances or undertaking selection and breeding activities. The value of A. lebbeck is critically dependent upon resistance to insect attack and this should be the first objective of developmental work on the species (`t Mannetje and Jones, 1992). Although the species has a very wide natural distribution and in that sense is not endangered, the blurring of boundaries between indigenous populations and those established from exotic germplasm is a conservation issue.

Reproductive Biology

The flowers of A. lebbeck are hermaphroditic, fragrant, white to greenish-yellow and borne in rounded, axillary clusters, 2-3.8 cm in diameter at the ends of lateral stalks. They have narrow, tubular, white corollas and numerous stamens. Wind is apparently the principal pollen vector, although the fragrant flowers attract large numbers of bees, which are likely to contribute to pollination (Parrotta, 1988; Lowry et al., 1994).

In cultivation, A. lebbeck can be established by direct sowing, using container-grown stock or as bare-rooted seedlings or stump plants (`t Mannetje and Jones, 1992; Gupta, 1993; MacDicken, 1994). The seeds are relatively large. Hocking (1993) reports 7000-12,000 seeds/kg while Lowry et al. (1994) note 7000-8000 seeds/kg. A. lebbeck is amenable to vegetative propagation by several means including tissue culture (Archna and Nangia, 1992), air layering (Misra et al., 1992; Misra and Jaiswal, 1995), stem cuttings (Rawat and Joshi, 1995), root explants (Miah and Rao, 1996) and as stump plants (Hocking, 1993).

Seeds of A. lebbeck may be sown without pre-germination treatment, although soaking the seeds in boiling water for 1 minute, followed by cool water for 24 hours, increases the germination rate. Germination of freshly extracted seeds in Puerto Rico was 60 to 90 percent; after 1 year of cold storage at 5 to 10°C, percentage germination dropped to 12 percent (Parrotta, 1988). However, seeds can be stored for up to 5 years in sealed containers at room temperature with only moderate reduction in percentage viability. Germination is epigeal, and generally occurs between 4 to 20 days after sowing, with peak germination at 12 to 18 days (Parrotta, 1988). In Puerto Rico, seedlings raised in plastic sleeves under light shade reached 20 to 30 cm height in 3 months (Parrotta, 1988). Seedlings develop a long, stout taproot at an early age, are drought-tolerant, and require only minimal weeding during the first months after planting (Parrotta, 2002). 

Physiology and Phenology

A. lebbeck is a perennial, deciduous tree. Annual height and stem diameter growth range from 0.5-2.0 m and 1.0-2.5 cm, respectively during the first 2-5 years of growth. Under suitable environmental conditions plants can grow 5 m/year. Trees usually attain a maximum height of up to 18 m (Parrotta, 1988). Trees growing in the dry tropics show a crown diameter expansion of 2-2.2 m/year until mature. Flowering can occur on plants as young as 10 months old (Cook et al., 2005).

A. lebbeck has a growth pattern strongly dependent on seasonal changes (`t Mannetje and Jones, 1992). It stops growing early in the dry season, loses its leaves in the middle of the dry season some 2 to 3 months later, remains leafless for 1 to 2 months, with new growth appearing towards the end of the dry season. Heavy flowering follows shortly afterwards, but seed set is initially poor (`t Mannetje and Jones, 1992). Further growth accompanied by flowering and good seed set occurs into the wet season. In northern Australia (within its natural distribution), flowering occurs from September to October and pods mature in May-July at the beginning of the dry season (Brock, 1988). Pods can remain on the tree for 3 to 4 months (`t Mannetje and Jones, 1992). In India, flowering occurs mainly from March to May, and fruits grow to their full size from August to October (Troup and Joshi, 1983). In Sudan, it flowers March-May and fruits May-August. In Tanzania, ripe pods can be found in July-December with a peak in August-October (PROTA, 2016). In Florida and the Caribbean, it flowers from April to September, but primarily in spring (or the onset of the rainy season), with pods held nearly throughout the year (Little and Wadsworth, 1964; Langeland et al., 2009). In China, it has been recorded flowering from May to September and fruiting from October to May of the following year (Flora of China Editorial Committee, 2016).

Associations

In the tropical dry and mixed deciduous forest of northern and central India, A. lebbeck is typically associated with the commonly dominant species Hardwickia binate and Tectona grandis. In West Bengal and Bangladesh, it is usually associated with species such as Salmalia malabarica [Bombax ceiba], Hymenodictyon excelsum [Hymenodictyon orixense] and Adina cordifolia. In the dry, deciduous scrub forests of southern India, it is often found with Santalum album, other Albizia species, and members of the genera Acacia, Ziziphus, Cassia and Terminalia. It also occurs as an aggressive colonizer in the dry forests of Punjab (both in Pakistan and India) dominated by Prosopis spicigera [Prosopis cineraria], Salvadora oleoides, and Capparis decidua (Venkataramany, 1968).

In Australia, associated dominants in semi-evergreen vine forests include Adansonia gregorii and Alphitonia excelsa. In semi-deciduous microphyll vine thicket on scree slopes of quartz sandstone mountains associate species include Paramygnia trimera, Celtis philippensis and Pouteria sericea (Miles et al., 1975). On lateritic plateaux, A. lebbeck grows with Hakea arborescens and Grevillea mimosoides in the shrub layer beneath low woodland and low open-forest. Dominant species are Eucalyptus tetrodonta, E. nesophila [Corymbia nesophila], Ficus spp. and Canarium australianum.

A. lebbeck fixes nitrogen after nodulating with a range of Rhizobium strains in many tropical soils, and does so at a rate that makes it an attractive hedgerow species for use in alley cropping (Kadiata and Mulongoy, 1995; Kadiata et al., 1996). This species is not Rhizobium specific and naturalized forms will produce nodules easily (Lowry et al., 1994). This species also forms symbiotic mycorrhizal associations between its roots and various fungi.

Environmental Requirements

A. lebbeck grows at elevations from sea level to 1500 m in a variety of climatic zones where annual rainfall ranges from 600 mm to 2500 mm, yet it will survive in areas with low and irregular rainfall receiving only 300 mm annually (`t Mannetje and Jones, 1992; Hocking, 1993; Lowry et al., 1994). In Australia, the distribution is in the hot humid climatic zone. Elsewhere it favours semi-arid to sub-humid areas (`t Mannetje and Jones, 1992). In Australia, the mean maximum of the hottest month is 30-35°C and the mean minimum of the coolest month is 19-31°C (Doran and Turnbull, 1997). The occurrence in the northern part of Australia has a marked monsoonal incidence of rainfall, with the 50th percentile rainfall being 1030-1755 mm, the 10th percentile being 720-1230 mm, while the lowest on record is 385-1050 mm. There are 75-125 days of rain per year; and the area is frost-free. In India, it is found in areas which experience temperatures up to 49°C, but it is also found in areas which experience frost, with an absolute minimum temperature of -5°C (Hocking, 1993).

Outside of Australia, it grows well on fertile, well-drained loamy soils but poorly on heavy cracking clays, and can tolerate moderately alkaline, saline and sodic (pH<9, ESP<35, ECe<4 dS/m) and lateric soils (Tomar and Yadav, 1982; Hocking, 1993; MacDicken, 1994; Singh, 1994; Parrotta, 2010; PIER, 2016). In Australia, the species occurs on the Kimberley plateau on soils overlying basalts (Miles et al., 1975) and amongst sandstone boulders and basalt outcrops on breakaway slopes. It is also found on the banks of streams on riverine sites (Beard, 1979), and on stabilized dunes or low lateritic ledges above the beach (Brock, 1988). Soil types include laterite and shallow sandy soils.

The timber of A. lebbeck is subject to borer and fungal attack while sapwood is liable to borers and termites but resistant to dry rot (Purdue University, 2017).

Damping off of seedlings in nurseries by Rhizoctonia solani [Thanatephorus cucumeris] has been recorded in India (Mehrotra, 1989) and Sri Lanka (Bandara, 1987) and by Fusarium spp. in India (Harsh, 1993). Occurrence of an unnamed virus disease on nursery plants of A. lebbeck has been reported by Chowdhery et al. (1992). Root rots, cankers, heart rots, spot fungi and rusts (e.g. Ravenelia) can cause damage (Sharma and Bhardwaj, 1988; Gupta, 1993; Lenné and Boa, 1994). Defoliation by Endothella albizae has been recorded in Africa, the Philippines and Pakistan (Gibson, 1975). Leaf blotch and foliar necrosis of A. lebbeck caused by Camptomeris albizae has been reported in tropical Africa, India, Sri Lanka, Pakistan, the Dominican Republic and Bangladesh (Browne, 1968; Gibson, 1975). Uromycladium tepperianum and Sphaerophragmium acaciae are found on A. lebbeck, as well as on other hosts including Acacia spp., but their importance has not been determined (Browne, 1968; Gibson, 1975; Bakshi, 1976). The leaf spot, Cercospora glauca was recorded on A. lebbeck in USA, China and Nepal, and C. albizae was recorded on A. lebbeck in India, Sudan and Tanzania (Gibson, 1975; Bakshi, 1976). A common spot disease, Colletotrichum lebbeck has been widely recorded on pods and leaves of A. lebbeck in Pakistan, the Philippines and Jamaica (Gibson, 1975). Young plantations in India may suffer serious defoliation by Phyllosticta albizinae (Bakshi, 1976). Dieback and canker are caused by Nectria ditissima [Neonectria ditissima] on A. lebbeck in Madagascar (Gibson, 1975). Fusarium solani [Haematonectria haematococca] causes greyish-black cankers and a severe infection will cause drying of the crown in 15-20 year-old trees in India (Bakshi, 1976). The most important disease of A. lebbeck is vascular wilt caused by Fusarium oxysporum f. sp. perniciosum. It is widespread in the USA and reported from Argentina and Puerto Rico (Gibson, 1975).

There is also a wide range of insect pests including sap suckers, wood and seed borers (such as Bruchidius spp.) and defoliators such as psyllids (probably Heteropsylla) (Hegde and Relwani, 1988; Ahmed et al., 1995). Insect predators associated with three species of psyllids infesting A. lebbeck in forest nurseries in India are reported by Thirumurthi and Annamali (1995). In Nigeria, damage has been caused by the striped mealy bug, Ferrisia virgata (Kadiata et al., 1992). Young leaves may be subject to heavy predation by the larvae of the grass yellow butterfly (Eurema hecabe) (Lowry et al., 1994); the effect is short-lived. Bark-feeding larvae of the longicorn beetle cause serious damage when complete girdling of stems 40-100 mm in diameter causes dieback (Lowry et al., 1994); little effect is seen in small and large stems. Individual trees exhibit considerable variation and may be more susceptible under water stress.

High seedling mortality may be caused by animal browsing and trampling (Hocking, 1993). In Australia, establishment can be adversely affected by grazing of young plants by mice, rabbits and other wildlife (`t Mannetje and Jones, 1992). Cheetal deer damage to nursery stock has been noted in Dehra Dun, India (Kumar and Thakur, 1993).

Animal feed, fodder, forage

• Fodder/animal feed
• Forage
• Invertebrate food for lac/wax insects

Environmental

• Agroforestry
• Boundary, barrier or support
• Erosion control or dune stabilization
• Revegetation
• Shade and shelter
• Soil improvement

Fuels

• Charcoal
• Fuelwood

Human food and beverage

• Honey/honey flora

Materials

• Carved material
• Dye/tanning
• Gum/resin
• Miscellaneous materials
• Wood/timber

Medicinal, pharmaceutical

• Source of medicine/pharmaceutical
• Traditional/folklore

Ornamental

• garden plant
• Potted plant
• Propagation material
• Seed trade

Charcoal

Containers

• Boxes

Furniture

Roundwood

• Posts

Sawn or hewn building timbers

• Flooring
• For light construction
• Wall panelling

Vehicle bodies

Veneers

Woodware

• Industrial and domestic woodware
• Tool handles
• Turnery
• Wood carvings

Albizia is very similar to Acacia. The former has stamens that are fused at the base, as opposed to free in Acacia (Lowry et al., 1994).

A. lebbeck shares similarities with A. retusa, which has fewer, white flowers in each of the flower clusters and narrower pods (Cowan, 2017).

Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

Control

Physical/Mechanical Control

Seedlings and saplings can be pulled out by hand or dug out, while larger, established trees are difficult to remove and must be cut and treated with herbicide (GISD, 2016; PIER, 2016). This species is known to be intolerant of continuous grazing by cattle (Lowry et al., 1994).

Chemical Control

For larger trees, chemical control is recommended in combination with cutting, by treating stumps with herbicide to prevent regeneration (GISD, 2016; PIER, 2016). In Brazil, the herbicide triclopyr has been recommended to control areas invaded by A. lebbeck (I3N-Brasil, 2016).

Research and the implementation of methods of prevention and intervention are urgently needed, especially considering the popularity of A. lebbeck as an ornamental and its potential for aggressive invasiveness.

01/03/17 Updated by:

Julissa Rojas-Sandoval, Department of Botany-Smithsonian NMNH, Washington DC, USA

Marianne Jennifer Datiles, Department of Botany-Smithsonian NMNH, Washington DC, USA

Pedro Acevedo-Rodríguez, Department of Botany-Smithsonian NMNH, Washington DC, USA