Grindelia camporum Seeds | Gumweed
LATIN NAME: Grindelia camporum
COMMON NAME: Gumweed
Plant Profile
Grindelia camporum is a sticky plant. The stems, the leaves and the bracts around the flower head are coated in a white resin that rubs off on the fingers and smells of turpentine and honey, and that resin is the reason the plant has a history. It grows as a bushy perennial or biennial to about a metre, with narrow, toothed leaves and yellow daisies that open in summer.
The species is native to the dry flats and alluvial washes of central California, and it colonises disturbed ground, roadside verges and the edges of fields. It is one of several gumweeds on the Pacific slope, and the group is hard to separate: G. camporum has a resinous head and a short ray floret, while G. hirsutula is hairier and G. stricta is taller and more coastal.
Science & Biotechnology
The resin is a mixture of diterpene acids, chiefly grindelic acid and its derivatives, together with flavonoids and small amounts of essential oil. The acids are labdane-type diterpenes, and they are what make the plant sticky and what give the extracts their antimicrobial activity in vitro. The concentration varies with the population and with the season, which is a problem for anyone trying to standardise an extract.
The plant is also a selenium accumulator on some soils, taking up the element from the parent rock and storing it in the tissue. That is a useful trait for remediation and a hazard for anyone eating the plant, since a forage sample from a seleniferous site can carry enough to poison livestock.
Uses & Benefits
Gumweed was a medicine of the American West. The resin was chewed or made into a tincture for bronchial complaints and for poison oak rash, and it appears in the pharmacopoeias of the nineteenth century as a treatment for asthma and for whooping cough. It is still sold as a tincture in the herbal trade, usually for the same complaints.
The plant was also tested as a source of industrial resin in the 1920s and 1930s, when the supply of imported gums was uncertain. The yield was too low and the harvest too seasonal to compete, and the work was abandoned. The seed is sold now as a bee forage and as a plant for dry, disturbed ground, where it establishes without help.
Growing from Seed
Seed needs light and a cool period. Surface-sow in autumn or give four weeks at 4 degrees, then sow at 18 to 20 degrees; germination is usually in two to three weeks. The seedlings are fast and can flower in their first year if sown early, and the plant self-sows freely once established.
Gumweed wants full sun, poor soil and no competition, and it resents being watered or fed. It is hardy to about minus fifteen and tolerates drought, salt and alkaline ground. Cut the stems back after flowering if self-sowing is not wanted, and wear gloves, since the resin is hard to wash off and can cause a rash on sensitive skin.
Our Take
A sticky, useful plant for poor ground and for bees, with a real history in Western herbal medicine and a resin that never quite became an industry.
Related Reading
Gardeners who grow Gumweed often pair it with these related subjects: