Calotropis is a small genus of large flowering shrubs in the family Apocynaceae (order Gentianales), first formally described in 1810. The genus is native to southern Asia and North Africa, with its two principal species — Calotropis gigantea and Calotropis procera — distributed across the Indian Subcontinent, Southeast Asia, China, the Middle East, and North Africa. Plants are commonly called milkweeds owing to the copious white latex they exude when cut.
Calotropis shrubs typically reach 2.4–3.0 m in height, occasionally exceeding 4.9 m. The leaves are sessile or sub-sessile, opposite, ovate, and cordate at the base. Flowers are 3.8–5.1 cm across, borne in umbellate lateral cymes, and range from white to pink (C. procera, fragrant) or white to purple (C. gigantea, unscented). Seeds are broadly ovoid and compressed, each bearing a tuft of long silky hairs that aids wind dispersal. Pollination is carried out by bees through a specialized gynostegium-and-pollinia mechanism in which pollen masses adhere to visiting insects and are transferred to the next flower.
The latex contains calotropin, a cardiac glycoside-like compound reported to be more toxic than strychnine, along with additional cardiac glycosides that deter browsing by cattle and other animals. Despite this toxicity, Calotropis species have a long history of use in traditional medicine across Asia and Africa, with applications including anti-inflammatory, antimicrobial, wound-healing, and analgesic treatments. The plant fibers (known as mudar or mader) have been used as a textile fiber, and the fragrant flowers are used in floral tassels in mainland Southeast Asian cultures. Calotropis species are often found on disturbed or abandoned farmland and are considered invasive weeds in parts of their range outside their native distribution.
Etymology
The genus name Calotropis derives from Greek roots, though the exact derivation is not documented in the sources consulted. The common name "milkweed" refers to the profuse white latex the plants produce when cut or damaged. Plant fibers from these species are traditionally called mudar or mader in South Asian languages.
Distribution
Calotropis is native to southern Asia and North Africa. Calotropis gigantea occurs across the Indian Subcontinent, Southeast Asia, and China; Calotropis procera extends further into the Middle East and North Africa, and is also naturalized in parts of tropical Africa and the Americas. Both species are typically found on disturbed ground, roadsides, and abandoned farmland.
Ecology
The toxic latex, containing calotropin and cardiac glycosides, deters most browsing mammals — cattle and other animals avoid the plants due to their bitter taste and toxic content. Bees are the primary pollinators, transferring coherent pollen masses (pollinia) via an adhesive gynostegium mechanism. Seeds are wind-dispersed on long silky hairs. Plants are pioneer colonists of disturbed, degraded, and abandoned agricultural land.
Cultural Uses
Across mainland Southeast Asia, the fragrant flowers of Calotropis are traditionally used in making floral tassels and garlands. The stem fibers, known historically as mudar or mader, have been used as a textile and cordage fiber in South Asia. In traditional medicine systems across Asia and Africa, various plant parts have been applied as anti-inflammatory, antimicrobial, wound-healing, analgesic, and anti-parasitic remedies, though clinical evidence for most uses remains limited and internal use carries significant toxicity risk.
