(1) Grindelia robusta Nutt.; (2) Grindelia squarrosa (Pursh) Dunal. Pharmacopoeial name: Grindelia. Other common names: (2) Broad-leaved gum plant, scaly grindelia.
Habitat and range: The gum plant (Grindelia robusta) occurs in the States west of the Rocky Mountains, while the broad-leaved gum plant (G. squarrosa) is more widely distributed, being of common occurrence on the plains and prairies from the Saskatchewan to Minnesota, south to Texas and Mexico, and westward to California.
Description: The name "gum plant" is applied especially to Grindelia robusta on account of the fact that the entire plant is covered with a resinous substance, giving it a gummy, varnished appearance. It is an erect perennial herb belonging to the aster family (Asteraceae) and has a round smooth stem, about 11/2 feet in height. The leaves are pale green, leathery in texture and rather rigid, coated with resin and showing numerous translucent dots, and are about an inch in length. In outline they are oblong spatulate that is, having a broad, rounded top gradually narrowing toward the base clasping the stem and with margins somewhat saw toothed. The plant branches freely near the top, each branch somewhat reddish and terminating in a large yellow flower. The yellow flowers are about three-fourths of an inch in diameter, broader than long, and are borne singly at the ends of the branches. Immediately beneath the flower is a set of numerous, thick, overlapping scales (the involucre), the tips of which are rolled forward, the whole heavily coated with resin.
The broad-leaved gum plant (Grindelia squarrosa) is very similar to G. robusta, except that it is smaller and less gummy in appearance. It is more sparingly branched near the top and the branches seem more reddish. The leaves are also clasping, but they are longer, about 2 inches in length, and broader, thinner in texture and not rigid, and more prominently toothed. The smaller flower heads are generally longer than broad and have narrower involucral scales, the recurved tips of which are longer and more slender.
Collection, prices, and uses: The leaves and flowering tops of both species of Grindelia are official in the United States Pharmacopoeia, and should be collected about the time that the flowers have come into full bloom. The price ranges from about 5 to 10 cents a pound. While both species are official, the leaves and tops of Grindelia squarrosa, being more prevalent, are generally used.
The odor of grindelia is balsamic and the taste resinous, sharply aromatic, and slightly bitter. The drug is sometimes used in asthmatic and similar affections, as a stomachic, tonic, and externally in cases of poisoning by poison ivy.
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