Albizia mollis Boiv.

Albizia julibrissin is a small to medium-sized tree 6-9 m tall with a spreading crown. The bark is light brown, nearly smooth, and generally thin with lens shaped areas along the stem. Leaves large, up to 50 cm long, bipinnately compound with 10-35 pairs of leaflets, many oblong leaflets, each only 6-12 mm long by about 7.5-10 cm wide, and alternate along the stems. Leaves fold up under the night sky Flowers showy, fragrant pink, about 3.75 cm long, that resembling pompoms and are arranged in panicles at the ends of branches. Fruits are flat, straw-colored pods about 15 cm long containing light brown oval-shaped seeds about 1.25 cm in length. The generic name commemorates the Florentine nobleman Filippo degli Albizzi, who introduced the plant into cultivation in the middle of the 18th century.

A. julibrisin is a hermaphroditic tree normally flowering from late spring to early summer, April to June in Nepal. Pods ripen in August-September and begin to disintegrate soon after, but remain on the trees into winter. Seeds are mostly dispersed below or around the parent plant, but can be dispersed further by water.

Prefers sandy loam-medium loam soil and can withstand high soil pH and salinity.

Prefers areas of high summer heat and is frost tolerant. In its native range, A. julibrissin prefers open sunny ravines. The Silk tree takes advantage of disturbed areas, often spreading by seed from nearby ornamentals or from contaminated fill dirt.

The silk tree is thought to be native from Iran to Japan. In 1749 F del Albizzi, the Florentian noble brought the species into cultivation in Europe. The silk tree was introduced to the USA in 1745 since then it has naturalized in the east and central USA and is found on a variety of sites in open areas. It is a highly invasive species and if possible other alternative landscaping plants should be sought.

The silk tree reproduces both vegetatively and by seed. They grow rapidly under good conditions but are short-lived and have weak, brittle wood. Using the direct seeding method seeds are sown in lines or patches usually before the monsoon rains in Asia. In Nepal entire planting uses 1 year old seedlings raised in the nursery in March-April, these are planted during the rains. If coppiced or top-killed, trees resprout quickly and sprouts can grow over 1m in a season. Stumps are planted during rains; the stumps are derived from 1 year old nursery grown seedlings.

The silk tree is fast growing, prefers full sun and wet soil. Seedlings transplant readily, and are very adaptable. The tree withstands drought, high pH, soil salinity and wind. Because of its aggressive colonizing attributes the silk tree can be an ecological threat to native species, some ways of curbing its spread include use of herbicides on young trees, bark girdling which is effective on large trees where the use of herbicides is impractical. Systemic herbicides such as glyphosate and triclopyr can kill entire plants.

A wilt disease caused by Fusarium oxysporum f.sp. perniciosum, has been reported in Greece and the USA. Agrilus sp. is the main stem-boring pest of A. julibrissin. Bruchidius terrenus is an important pest of A. julibrissin in Taiwan and China. Other identified pathogens are Heterosporium albizziae and silk tree leaf rust Haploravenelia japonica causing silk tree leaf spot. A canker disease caused by an unidentified species of Fusicoccum causes great damage to trees. The root-knot nematode, Meloidogyne incognita also ataacks the silk tree.

Silk tree seeds have impermeable seed coats that allow them to remain dormant for many years. One study showed that 90% of the seeds were viable after 5 years. The optimum treatment time for A. julibrissin with sulphuric acid (specific gravity 1.84) was 40 minutes, yielding 98% germination. In an experimental trial germination of scarified seeds was 90% or over in all media; germination of non-scarified seeds was lowest (3%) in sterile agar and significantly higher in non-sterilized soil (30%).

Erosion control: Cultivated on terrace edges in the Himalayas to prevent soil erosion. Shade or shelter: Provides shelter in gardens. Reclamation: Withstands drought and can adapt well in arid conditions. In Korea Republic the silk tree is a recommended native species for revegetation of felled forest slopes. Nitrogen fixing: Enhances soil fertility by nitrogen fixation. Soil improver: Leaf litter of the silk tree on decomposition replenish soil nutrients. In an experimental trial in the USA nutrient input-output balance of N, P, K, Ca and Mg was higher for alley cropping with A. julibrissin than for non-alley cropping systems. Ornamental: The attractive fragrant/ pink flowers and fern-like leaves of mimosa leaves, which stay green until killed by frost make it an ideal landscape plant. Intercropping: A. julibrissin should be avoided in intercropped systems, dense stands of mimosa severely reduce the sunlight and nutrients available for other plants.

Fodder: The leaves are used as fodder. Apiculture: The flowers provide nectar and pollen for bees. Timber: The wood is used in furniture making. Poison: Toxic amino acids in the seeds repelled or killed larvae of the polyphagous pest Prodenia eridania (Noctuidae). Crude saponin fraction of stem bark of A. julibrissin demonstrated cytotoxicity. Medicine: The dried stem bark of A. julibrissin is used medicinally in China in the preparation of tonics and sedatives. Other products: Leaf extracts of A. julibrissin digest casein components of milk resulting in large peptide fragments. A. julibrissin is the host of the lac insect [Laccifer lacca] which colonizes its shoots, feeding on accumulated carbohydrates. The insect produces lac used in the manufacture of lacquering material. Fertilizer treatments resulted in greater production of lac by L. lacca.