Chilean tarweed (Madia sativa) is the second “sticky” plant I recently found in our east pasture in Modoc County CA. (The first was catchfly.) Also commonly called coast tarweed, this member of the sunflower family was native to South America. It now can be found along the entire Pacific Coast and in some eastern and midwestern states. Chilean tarweed thrives in disturbed places such as roadsides, overgrazed rangelands or open, dry hillsides. Difficult to eradicate and often forming dense stands, Chilean tarweed is considered a noxious weed by farmers and range managers, while to others it is a pretty wildflower.
An annual with erect stems that are either simple or branching, the entire plant is sticky – glandular and hairy. It IS tacky to the touch! The narrow leaves can be entire or slightly toothed. The flowering heads are clustered at the apex of the stem, at the ends of stem branches or in leaf axes. Partially enclosed by leaves, the ray and disk flowers are both bright yellow. The number of ray flowers can vary, but usually there are two to five. Chilean tarweed has a strong, pungent odor that is supposed to resemble tar. Although the aroma is reported to be unpleasant, I personally do not mind the odor and actually find it rather interesting. After walking through a patch of Chilean tarweed the scent will remain on clothing for hours.
Chilean tarweed was once grown as a crop in South America where a highly nutritious oil was pressed from the seeds. Native peoples in California also collected the seeds for winter use. I am not certain how they managed to handle such a sticky plant.
The genus name, Madia, derives from the Chilean name for this plant, “madi”. The species name, satvia, meaning “sown” in Latin, recalls that this plant was once cultivated. The common name tarweed either refers to the “tarlike” scent or the fact that tar is sticky or both. I opt for the sticky tar theory since as a curious pre-teen, when one could still walk directly up to (and er, into) the La Brea Tar Pits (California), I learned firsthand how tacky tar can actually be.