- This page is about the tree described by Antonio Durazzini. John Gilbert Baker used the same scientific name to refer to Prain's Albizia kalkora, the Mimosa kalkora of William Roxburgh.
|Persian Silk Tree|
Not evaluated (IUCN 3.1)
Durazz., 1772 non sensu Baker, 1876
Many, see text
The genus is named after the Italian nobleman Filippo degli Albizzi, who introduced it to Europe in the mid-18th century, and it is sometimes incorrectly spelled Albizzia. The specific epithet julibrissin is a corruption of the Persian word gul-i abrisham (گل ابریشم) which means "silk flower" (from gul گل "flower" + abrisham ابریشم "silk").
Albizia julibrissin is known by a wide variety of common names, such as Persian silk tree or pink siris. It is also called Lenkoran acacia or bastard tamarind, though it is not too closely related to either genus. The species is usually called "silk tree" or "mimosa" in the United States, which is misleading - the former name can refer to any species of Albizia which is most common in any one locale. And, although once included in Mimosa, neither is it very close to the Mimoseae. To add to the confusion, several species of Acacia, notably Acacia baileyana and Acacia dealbata, are also known as "mimosa" (especially in floristry), and many Fabaceae trees with highly divided leaves are called thus in horticulture.
Its leaves slowly close during the night and during periods of rain, the leaflets bowing downward; thus its modern Persian name shabkhosb (شبخسب) means "night sleeper" (from shab شب "night" and -khosb خسب "sleeper"). In Japan its common names are nemunoki, nemurinoki and nenenoki which all mean "sleeping tree". Nemu tree is a partial translation of nemunoki.
A. 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 bipinnate, 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 small calyx and corola (except the central ones), and 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:
- A. julibrissin var. julibrissin. The typical variety, described above.
- A. julibrissin var. mollis. Differs in the shoots being densely hairy.
Cultivation and uses
A. julibrissin is widely planted as an ornamental plant in parks and gardens, grown for its leaf texture and flowers. The broad crown of a mature tree makes it useful for providing dappled shade. The flower colour varies from white in A. julibrissin f. alba, to rich red-tipped flowers. Variants with cream or pale yellow flowers are also reported. Other cultivars are becoming available: 'Summer Chocolate' has red foliage ageing to dark bronze, with pale pink flowers; 'Ishii Weeping' (or 'Pendula') has a drooping growth habit.
A. julibrissin f. rosea
There is also a form, A. julibrissin f. rosea (pink silk tree) which has, in the past, been classed either as a variety or as a cultivar. This is 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 typical form, surviving temperatures down to at least -25 °C. 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. In Japan, A. julibrissin f. rosea is often used for non-traditional bonsai. The name nemunoki*(Jap. ねむの木, Kanji: 合歓木) and its variants is a kigo representing the summer in haiku, especially a sleepy summer evening.
A. julibrissin has been found to possess antidepressant effects in mice, most likely mediated through 5-HT1A receptors. In traditional Chinese medicine Albizzia jublibrissin (合歡花 He Huan Hua) is used to nourish the heart and calm the spirit.
In the wild, the tree tends to grow in dry plains, sandy valleys, and uplands. It has become an invasive species in Japan; and in the United States it has spread from southern New York, New Jersey and Connecticut, west to Missouri and Illinois, and south to Florida and Texas. It is cultivated in California and Oregon, but its high seed production and almost virulent level of viability has made it a weed in many areas; see also tree of heaven.
This tree is bold and strong in its invasive ability. It is allelopathic to its neighbors and undergrowth (although Miner's Lettuce seems to thrive in its shadow in cool moist climates). Its seeds are as numerous as they are especially fertile, even over long periods of drought. Each pod, which resemble a flattened bean pod made of paper, contains an average of 8 seeds. These pods are produced in abundance. They are designed to release a burst of pods with every strong wing, and to carry over surprisingly long distances. The tree never seems to be without at least a few remnant pods. And the pods themselves fall apart very rapidly if not gathered and destroyed, thus spreading seeds into every nook and cranny. In lawns, if not plucked by hand or poisoned, they can sprawl beneath a tall cut.
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, being highly susceptible to mimosa vascular wilt, a fungal disease caused by a species of Fusarium, though the 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.
- (Japanese) "合歓の花（ねむのはな） 晩夏". http://kigosai.sub.jp. Retrieved 2011-06-27.
- Kim, JH; Kim, SY; Lee, SY; Jang, CG (2007). "Antidepressant-like effects of Albizzia julibrissin in mice: Involvement of the 5-HT1A receptor system". Pharmacology, Biochemistry, and Behavior 87 (1): 41–7. doi:10.1016/j.pbb.2007.03.018. PMID 17477962.
- Albizza (合歡皮) Acupuncture and Chinese Medicine Ap. 2012
- COSTA, Paulo Pedro P. R. Plantas calmantes, história e composição química. Acupuntura, ciência e profissão April 2012 (pt)
- TIERRA, Michael. Albizzia: The Tree of Happiness. For many, an effective natural approach for the treatment of mild states of depression and anxiety. Planetary Herbology. Planet Herbs (Apr. 2012)
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