This subgroup within the family Apocynaceae includes approxi- mately 240 genera of herbs, shrubs, and climbers, which are widely dis- tributed in tropical and temperate regions. leaves are simple, entire, often reduced, and opposite or whorled. This group lacks the char-acteristic salverform or funnel-shaped corolla of the traditional Apocynaceae genera. Flowers are hithly modified. The pollen grains are usually clumped in sticky masses called pollinia (orchids also have pollinia). Upon close inspec-tion, the flowers structures are quite marvelous, if not bizarre. The milky sap may be irritating to some people. milkweeds, familiar wildflowers of the United States, belong in this group. The fruits are paired pa-pery follicles. Silky tufts are at-tached to the seeds, which are easily carried away in the wind. Most species in this group attract monarch and viceroy butterflies.
Calotropis includes 3 species of shrubs or trees from india and Africa. They are sometimes culti-vated for their strong fiber and for the downlike silky hairs attached to the seeds and used as stuffing ma-terial. They have become natural-ized in some areas where they were introduced. Biochemicals are pro-duced from the milky, poisonous latex. The highly modified stigma and stamens sug-gest an elaborate crownlike structure in the center of the flower. The globular fruit has a spongy pericarp. These xeric plants thrive in hot, dry loca-tions but also do well in humid cli-mates with excellent drainage. Plants are salt tolerant to the dunes.
Crown-flower, bowstring hemp, lechoso
Synonym: Asclepias gigatea. China to India, Sri Lanka, Indonesia. Evergreen spreading shrubs to 15 ft, zones 10-11. Blooms intermittently in warm months. moderate moisture to seasonally dry. Gritty, well-drained soil. Full sun. flowers: rotate, to 1.5 in . wide, lavender. leaves: obovate, to 8 in. long, woolly, veins light. Stems: covered with white woolly hairs. Suitable for large containers. Attractive to monarch butterflies. Colotropic procera, widely naturalized in the tropics, is distinguished by its white petals with dark purple tips.