Calotropis is a genus of plants within the asclepiadaceae, or milkweed, family. This genus includes two species of milkweed, Calotropis gigantea or giant milkweed and Calotropis procera or roostertree. Milkweeds are named for the milky-colored sap contained within the stems and leaves. Many people are allergic to the sap, and the plant itself is highly toxic.
Giant milkweed, or Calotropis gigantea, can grow to be 16 feet (about 5 meters) tall and has clusters of lavender flowers at the branch tips. It is native to Africa, Asia, Australia, and the Caribbean where it grows near roadsides, beaches, and other neglected areas. In addition to drought tolerance, the calotropis thrives in salty soil. These flowering plants do best in sunny areas, and will not grow well in the shade. This plant is a prolific seeder and is easy to propagate which increases its potential to become an invasive plant.
Roostertree or Apple of Sodom grows in tropical regions. The trees are 10 to 15 feet (3-4.5 meters) tall when mature and covered with a corky bark. Instead of flowers, this plant produces clusters of three to four round, green fruits that appear similar to an apple or an orange, but can't be eaten.
The "apples" are mostly hollow and pop when pressure is applied. A seed pod and a small amount of silky fibers are contained within the fruit. Jamaicans collect this silk for pillow stuffing, while Arabs twist it into gun matches. The Calotropis procera fruit also contains the milky sap that gives these plants their name. The sap is highly poisonous and contains chemicals that are considered steroidal heart poisons.
Although all calotropis plants are toxic, these poisonous plants have beneficial uses as well. The durable fiber produced by the calotropis is used to create ropes, carpets, fishing nets, and sewing thread. A combination of fermented milkweed and salt can be used to remove hair from goat and sheep skins during the leather-making process. Calotropis has also been used as a fungicide and insecticide.
As a medicinal plant, milkweed has unique properties. When combined with other medicines, it is useful to treat a large variety of conditions including fevers, indigestion, colds, asthma, and nausea. The entire plant can be dried and used as a tonic and expectorant. Dried root bark from the milkweed plant is used as a depurative, expectorant, and laxative. The leaves can relieve intermittent fevers, swelling, paralysis, and arthralegia, while the flowers can be used as an astringent and to aid in digestive issues.