Salix babylonica (Babylon willow or weeping willow; Chinese: 垂柳; Pinyin: chuí liǔ) is a willow species native to the drier areas of northern China, Korea, Mongolia, Japan, and Siberia, but has been cultivated for thousands of years elsewhere in Asia, traded along the Silk Road to Southwest Asia and Europe. Babylonica has been cultivated in China since at least the 3rd century BC. From there, plant material spread via the Silk Road to Southwest Asia and Europe. It was introduced to England in the 18th century. Kew Botanical Garden records mention that it is now common in the UK, while global invasion databases emphasize its use for erosion control and its ability to spread vegetatively.

Salix babylonica, also known as the weeping willow tree, thrives in a moist and well-drained environment, with exposure to full sun to partial shade. The ideal temperature for this plant ranges from 5 to 35 degrees Celsius.

• Root: Strong and aggressive; roots can spread far from the tree base and often seek out water sources (due to its high tolerance for moist soil).

• Branches: Thin, long, very flexible, and pendulous (weeping); the color of young branches ranges from reddish to yellowish or brown. The surface of the twigs is usually smooth (glabrous). Very flexible branches are often seen on young cultivars.

• Leaves: Arrangement: simple, alternate. Shape: narrow, linear–lanceolate (lanceolate to linear-lanceolate) with a sharp tip (acuminate). Size: typically 7–14 cm long (variation among sources and cultivars; many reports state 3–6 inches / ≈7–15 cm). Margin: finely serrated. Surface: light green to green on the upper side; the underside is paler or slightly bluish/grayish (glaucous). Many sources note the leaves are relatively thin. Young leaves are sometimes finely hairy, which is lost as they mature. Phenology: emerges in spring; leaves turn yellow before falling.

• Flower: In the form of catkins that appear just before or simultaneously with the emergence of leaves in spring. Catkins are relatively small (about 1–5 cm in various reports), yellow to greenish when blooming; they look 'fuzzy' due to the perianth/stamens/filaments on the flower.

• Fruit: After pollination, small capsules are formed containing many small seeds encased in cottony hairs, allowing them to be easily dispersed by the wind.

• Propagation: Done generatively using seeds.

• Propagation: Done vegetatively using stem cuttings.

Analgesic (pain reliever), antipyretic (fever reducer), anti-inflammatory (anti-swelling), as well as some antioxidant, antibacterial, and potential antitumor activity in preliminary research. Used for fever, headache, and joint pain/rheumatism, wounds, abscesses, and skin infections.

• Salicin (a precursor to salicylate/aspirin), flavonoids, tannins, and other phenolics, & procyanidins.