Calotropis procera is a resilient shrub, often recognized by common names such as giant milkweed, Sodom apple, or roostertree. An evergreen perennial of the milkweed family, it thrives in arid and semi-arid regions across various continents.
Identification and Habitat
Calotropis procera grows as an upright shrub, typically 6 to 8 feet tall, though some reach 15 feet. Its stems are soft-wooded with rough, corky bark and produce a milky latex when broken. Its large, grey-green, waxy leaves are oblong-obovate to nearly circular (3-7 inches long, 2-5 inches wide), with short-pointed to blunt tips, bases that nearly clasp the stem, and dull white veins.
Its distinct flowers appear in clusters of 3 to 15, each 1 to 2.5 cm across. They are waxy and shallowly bell-shaped, with petals ranging from pale purple to white and dark purple or purplish tips. After flowering, it produces large, inflated, grey-green fruits that turn brown when mature. These fruits contain numerous seeds, each with tufts of long, silky hairs for wind dispersal.
Native to Africa, the Arabian Peninsula, and Southern Asia, Calotropis procera has naturalized globally, found in regions such as Australia, various Pacific Islands, and parts of Central and South America, including California and Hawaii. This plant flourishes in open, disturbed habitats like overgrazed pastures, rangelands, roadsides, river flats, and coastal dunes, showcasing its adaptability.
Traditional and Folkloric Uses
Calotropis procera has been widely used in traditional medicine systems across North Africa, the Middle East, and South and Southeast Asia, including Ayurveda. Different parts of the plant, such as its milky latex, leaves, flowers, and roots, were traditionally employed for therapeutic properties. The milky juice, for instance, was used in some practices as an abortifacient or infanticide.
Traditional applications addressed various ailments. The plant’s leaves were sometimes used in fomentation and for insecticidal properties. Extracts from the plant have been applied for skin conditions, digestive problems, and respiratory issues like asthma. Roots and flowers were also used for fevers and general discomforts.
Beyond medicine, Calotropis procera has other traditional uses. The wood yields a fibrous substance used to make rope and cordage. From the seeds, its soft, silky floss was used as stuffing.
Toxicity and Precautions
The milky latex of Calotropis procera is its primary source of toxicity, containing cardiac glycosides. Examples include calotropin, calotoxin, calactin, uscharidin, and voruscharin, similar to those in foxgloves. These compounds interfere with cardiac function, risking humans and livestock.
Direct contact with the milky sap causes severe health risks. Skin exposure may lead to irritation, redness, and blistering. Eye contact is particularly dangerous, resulting in severe inflammation, burning, and potential temporary vision loss or corneal damage. Cases of corneal damage are documented from children touching the sap and then their eyes.
Ingestion of any part, especially the latex, leads to severe systemic effects. Symptoms in humans and animals include nausea, vomiting, diarrhea, abdominal pain, and cardiac irregularities. It is a significant livestock poison, capable of causing illness or death in grazing animals. Extreme caution is advised when handling this plant.
Ecological Significance
Calotropis procera plays a dual role in ecosystems. It functions as a hardy pioneer species, colonizing and stabilizing degraded, overgrazed, or arid lands. Its ability to thrive in harsh conditions makes it valuable for reclaiming disturbed areas, establishing quickly and preventing soil erosion. Its resilience allows it to grow along roadsides, in river flats, and coastal dunes.
Despite its role in land stabilization, Calotropis procera is an aggressive invasive species in many non-native environments. In these regions, it forms dense, impenetrable thickets that outcompete native vegetation, reducing biodiversity and altering local ecosystems. This invasive potential is a concern where it has been introduced outside its natural range, such as Australia and the Americas.
On a positive note, Calotropis procera serves as a host plant for certain butterfly larvae. It is a larval food plant for Danaid butterflies, including the common tiger butterfly (Danaus chrysippus). This relationship supports the life cycle of these insect populations.