Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)

Department / School



A species of Grindelia known as Gum, Rosin or Tar weed, is of common occurrence on dry banks and sandy soils in various parts of South Dakota. During day seasons it attains such a dense growth in closely cropped pastures that horses feeding in them have their heads and manes covered with a black tarry-like substance, and their fetlocks collects fairly large ball of this tarry mass. In dry years the development of the weed is so rapid that the grass in a closely cropped pasture may be nearly exterminated during a single season. A pasture may seem to be entirely freed from Grindelia for several rainy years when one season of drought will cause it to develop a thick stand. It yields to cultivation readily, attaining the height of three feet. It has never been noticed by the writer in virgin sod, and early settlers of fifty or more years ago, do not remember having seen it at that time. This leads to an interesting question. How did Grindelia become naturalized in South Dakota? It has been observed that this drought resisting plant usually follows the course of rivers. Perhaps it entered South Dakota in the manner or admixed with grass or clover seed. The hardy nature of the plant may be attributed to its resinous nature. Pammel in his Manual of Poisonous Plants states that animals do not like it, so that cases of animal poisoning by Grindelia are quite rare. Because of the common occurrence of this drug plant in South Dakota, it was deemed advisable to make a study of same from various standpoints, to determine whether or not it was one of the three species of Grindelia as recognized by the Ninth Decennial Revision of the United States Pharmacopoeia, and if so, the commercial possibilities that its collection and marketing offered, as well as to make a chemical and morphological study of the plant. (See more in text)

Library of Congress Subject Headings

Grindelia squarrosa


Includes bibliographical references (page 56)



Number of Pages



South Dakota State College


No Copyright - Non-Commercial Use Only