The gumweed belongs to the composite family. The surface of the stem, leaves and flowers are covered with a sticky resin, which is where the name "gumweed" comes from. There are about 60 different species of gumweed. Three species are used phytotherapeutically: the California gumweed (Grindelia camporum Green; syn.: G. robusta Nutt.), the bulky gumweed [G. squarrosa (Pursh) Dunal] and the hairy gumweed (G. hirsutula Hook et Arn.; syn.: G. humilis Hook. et Arn.).
The biennial plants bear yellow flowers up to 5 cm across, covered with a whitish resin. Flowering time is May to June.
The dried flowers, leaves and stems are used phytotherapeutically(Grindelia herba - Grindeliaherb ).