Albizia julibrissin
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 Persian Silk Tree foliage and flowers
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| Albizia julibrissin (Willd.) Durazz. |
Albizia julibrissin is a species of legume in the genus Albizia, native to southern and eastern Asia, from Iran east to China and Korea.
The genus is named after the Italian nobleman Filippo del Albizzi, who introduced it to Europe in the mid 18th century, and it is sometimes incorrectly spelled "Albizzia". The specific name julibrissin is a corruption of the Persian word Gul-i Abrisham (گل ابریشم) which means the silk flower ("Gul" گل means "flower" and "Abrisham" ابریشم means "silk").
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[edit] Common names
Albizia julibrissin is known by a wide variety of common names, such as Persian Silk Tree, Pink Siris, Bastard Tamarind or Nemu tree. Its leaves slowly close during the night and during periods of rain, the leaflets bowing downward as if the tree were sleeping: its modern Persian name, Shabkhosb (شبخسب), means "the night sleeper" ("shab" شب means "night"; Khosb خسب means "sleeper", when used as a suffix). In Japan its common names are Nemunoki, Nenenoki and Nemurinoki which all mean "sleeping tree"; the name represents the summer in haiku. The tree is usually called Mimosa in the United States, which is misleading because, although once included in Mimosa and related to it, it is no longer classified in that genus. (To add to the confusion, several species of Acacia, notably Acacia baileyana and Acacia dealbata, are also known as "mimosa", especially in floristry).
[edit] Description
Albizia julibrissin is a small deciduous tree growing to 5–12 m tall, with a broad crown of level or arching branches. The bark is dark greenish grey in colour and striped vertically as it gets older. The leaves are tripinnate, 20–45 cm long and 12–25 cm broad, divided into 6–12 pairs of pinnae, each with 20–30 pairs of leaflets; the leaflets are oblong, 1–1.5 cm long and 2–4 mm broad. The flowers are produced throughout the summer in dense inflorescences, the individual flowers with no petals but a tight cluster of stamens 2–3 cm long, white or pink with a white base, looking like silky threads. They have been observed to be attractive to bees, butterflies and hummingbirds. The fruit is a flat brown pod 10–20 cm long and 2–2.5 cm broad, containing several seeds inside.
There are two varieties:
- Albizia julibrissin var. julibrissin. The typical variety, described above.
- Albizia julibrissin var. mollis. Differs in the shoots being densely hairy.
There is also a form, Albizia julibrissin f. rosea (which has, in the past, been classed either as a variety or as a cultivar). A smaller tree, only growing to 5–7 m tall, with the flowers always pink. Native to the northeast of the species' range in Korea and northern China, it is more cold-tolerant than the type, surviving temperatures down to at least -25 °C.
[edit] Cultivation and uses
Persian Silk Tree is widely planted as an ornamental plant, grown for the leaf texture and flowers. The broad crown of a mature tree makes it useful for providing dappled shade.
In the wild, the tree tends to grow in dry plains, sandy valleys, and uplands. It has become an invasive species in Japan and the United States, in the latter widely spread from Long Island, New York west to Missouri and Illinois and south to Florida and Texas; it is also cultivated in California and Oregon but is not invasive there. Breeding work is currently under way in the United States to produce ornamental plants which will not set seed and can therefore be planted without risk. However, in the eastern United States it is generally a short-lived tree as this species is highly susceptible to mimosa vascular wilt, a fungal disease caused by a species of Fusarium. (Ironically, this disease does not seem to have seriously impacted its populations.) Because of its invasive tendencies and disease susceptibility, it is rarely recommended as an ornamental plant in the US, though it is still widely planted in parts of Europe.
The flower colour of Albizia julibrissin varies from white, in A. julibrissin f. alba, to rich red-tipped flowers; cream- or pale yellow-flowered variants are also reported. Seedlings vary: those with darker pink flowers than the normal A. julibrissin are classed as A. julibrissin f. rosea, but some may be paler than others; the selected cultivar A. julibrissin 'Ernest Wilson' (also known as 'E.H.Wilson' or 'Rosea') is a cold-tolerant tree with deep pink flower colour. Other cultivars are becoming available: A. julibrissin 'Summer Chocolate' has red foliage ageing to dark bronze, with pale pink flowers; A. julibrissin 'Ishii Weeping' (or 'Pendula') has a drooping growth habit.
In Japan, Albizia julibrissin f. rosea is often used for non-traditional bonsai.
The bark or cortex is used to cure bruises and as a vermicide. The seeds are used as a food for livestock and wildlife, and the sweetly-scented flowers are a good nectar source for honeybees.
