Silk Tree

Albizia julibrissin is native to a broad region spanning from Iran and the Caucasus through Central Asia to China, Korea, and Japan.

• Originally from open woodland, forest edges, and disturbed areas across southwestern and eastern Asia
• First introduced to Europe in the mid-18th century by Filippo degli Albizzi, who brought it from Constantinople to his garden near Florence, Italy
• Rapidly became a fashionable ornamental tree in European gardens during the late 18th and 19th centuries
• Introduced to the United States in 1785 as an ornamental and has since naturalized across much of the Southeast
• Also introduced to many other temperate and subtropical regions worldwide
• In its native range, grows at elevations from sea level to approximately 1,500 meters
• The species has been cultivated in Chinese and Japanese gardens for centuries, where it is valued for its elegant form and summer flowers

Albizia julibrissin is a small to medium-sized deciduous tree with a broad, flat-topped crown and spreading branches.

Size and habit:
• Typically grows 5 to 12 meters tall with a spread of 5 to 10 meters
• Crown is vase-shaped when young, becoming broadly spreading and flat-topped with age
• Trunk is short, typically 20 to 40 cm in diameter, with smooth, grayish-brown bark
• Branches are spreading, often slightly pendulous at the tips

Leaves:
• Large, bipinnately compound, 20 to 45 cm long, with 8 to 20 pairs of pinnae
• Each pinna bears 20 to 40 pairs of tiny oblong leaflets, 5 to 12 mm long
• Leaflets are dark green above, paler below, and fold closed at night (nyctinasty) and during rain
• Leaves give the canopy a fine-textured, fern-like appearance

Flowers:
• Produced in dense, terminal, powder-puff-like heads, 3 to 5 cm in diameter
• Individual flowers lack typical petals — the showy parts are actually long, silky stamens
• Stamens are pink to deep pink at the tips, white toward the base, creating a gradient effect
• Extremely fragrant, blooming prolifically in June through August
• Flowers attract bees, butterflies, and hummingbirds in abundance

Fruit:
• Flat, straw-colored pods 10 to 20 cm long and 1.5 to 2.5 cm wide
• Pods persist on the tree through winter, sometimes into the following spring
• Each pod contains 5 to 10 flat, brown, oval seeds

Albizia julibrissin is an adaptable species that occupies a range of habitats in both its native and introduced ranges.

Habitat:
• In its native Asia, grows in open woodlands, forest margins, grasslands, and along stream banks
• Highly tolerant of drought, poor soils, and urban pollution
• Prefers full sun but tolerates partial shade
• Grows in a wide range of soil types including clay, loam, and sandy soils
• Tolerates salt spray and is sometimes planted in coastal areas

Ecological role:
• Nitrogen-fixing through symbiotic rhizobia, improving soil fertility
• Flowers are an important nectar source for bees and butterflies during midsummer
• Seeds are eaten by birds and small mammals
• Provides nesting habitat for birds in its spreading canopy
• Considered invasive in the southeastern United States, Japan, and parts of Africa, where it can form dense thickets that suppress native vegetation
• Can sprout vigorously from root suckers after damage, making it difficult to control where unwanted

Listed as Least Concern globally due to its wide distribution across Asia.

• Common and secure throughout its native range in Asia
• Has become invasive in several regions including the southeastern United States, where it threatens native plant communities
• In the US, it is listed as a noxious weed in several states
• Control measures include cutting, girdling, and herbicide application to prevent spread into natural areas
• Some cultivars have been developed with reduced seed production to minimize invasive potential

Planting:
• Propagation from seed or by cuttings
• Seeds require scarification — soak in hot water or nick with a file to break dormancy
• Sow seeds in spring after last frost; germination in 7 to 14 days
• Semi-hardwood cuttings taken in summer root readily with rooting hormone
• Fast-growing, often flowering within 2 to 3 years from seed
• Prefers full sun and well-drained soil
• Adaptable to a wide range of soil pH and types
• Hardy to USDA zones 6 through 10
• Drought-tolerant once established
• Prune in late winter to maintain shape and remove dead wood
• Relatively pest-free, though susceptible to mimosa wilt (Fusarium oxysporum f. sp. perniciosum), a vascular wilt disease that can kill trees
• Avoid planting near natural areas where it may become invasive
• Consider sterile cultivars such as 'Summer Chocolate' or 'Ombrella' to reduce invasive potential

Uses:
• Widely planted as an ornamental tree for its showy flowers and fern-like foliage
• Provides excellent shade in small to medium-sized gardens
• Used in traditional Chinese medicine — bark (known as "he huan pi") is used to treat depression, anxiety, and insomnia
• Flowers (known as "he huan hua") are used in traditional Chinese medicine for similar calming purposes
• Modern research has confirmed anxiolytic and antidepressant properties in bark and flower extracts
• Wood is used for fuel and making small items
• Leaves are occasionally used as emergency livestock fodder
• Planted as a soil-improving species due to nitrogen fixation
• Used in land reclamation and erosion control projects
• Young leaves and flowers are edible when cooked in some Asian cultures