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tarweed,any of several related resinous herbs (chiefly species of Hemizonia and Madia) of the family Asteraceae (asteraster
[Gr.,=star], common name for the Asteraceae (Compositae), the aster family, in North America, name for plants of the genus Aster, sometimes called wild asters, and for a related plant more correctly called China aster (Callistephus chinensis
..... Click the link for more information. family), having strongly scented and sticky herbage. Most North American species are found in fields and on dry hillsides of the Southwest and the Pacific region. They bear daisylike heads of yellow or cream-colored flowers. The heads of the common tarweed (M. elegans, also called common madia) are marked with an inner red ring and, like those of other Madia species, open in the evening and close before noon. Several species of this genus, notably M. sativa of Chile, are cultivated as oilseeds. Similar related Western plants are the rosinweeds (Calycadenia) and the gumweeds, or sticky-heads (Grindelia). Several gumweed species have become established in the East, where they are sometimes called tarweeds. The dried herbage of some gumweeds, containing resinous substances and essential oils, has been used in domestic remedies for treating burns and ivy poisoning. Tarweeds are classified in the division MagnoliophytaMagnoliophyta
, division of the plant kingdom consisting of those organisms commonly called the flowering plants, or angiosperms. The angiosperms have leaves, stems, and roots, and vascular, or conducting, tissue (xylem and phloem).
..... Click the link for more information. , class Magnoliopsida, order Asterales, family Asteraceae.