The gum plant belongs to the composite family. The surface of the stems, leaves and flowers are covered in a sticky resin, which is where the name "gumwort" comes from. There are around 60 different types of gumwort. Three species are used phytotherapeutically: the Californian gum plant (Grindelia camporum Green; Syn.: G. robusta Nutt.), the bulky gum plant [G. squarrosa (Pursh) Dunal] and the hairy gum plant (G. hirsutula Hook et Arn.; Syn.: G. humilis Hook. et Arn.).
The biennial plants bear yellow flowers up to 5 cm in size, which are covered in a whitish resin. Flowering time is May to June.
The dried flowers, leaves and stems(Grindelia herba - Grindelia herb) are used phytotherapeutically.