Western Ragweed (Ambrosia psilostachya) is a perennial herb in the aster family that is infamous for its propensity to cause hay fever. Rated 10 out of 10 on theOgren Plant Allergy Scale, it is included on nearly all local allergy tests. Western Ragweed is native to all of Woodland and to all the parts of Yolo County that are in the Sacramento Valley flatlands. It can grow to 7 feet tall and 1 foot wide but is more often seen at under 3 feet tall. It prefers full sun and usually grows in dry areas. It goes semi-deciduous in winter.
If you know you're allergic to ragweed, you may want to avoid planting closely related plants in your garden. Ragweed is a member of the ragweed subtribe (Ambrosiinae) of the sunflower tribe (Heliantheae) of sunflower supertribe (Helianthodae) of the aster subfamily (Asteroideae) of the aster family. Sunflowers are by far the most common garden plant in the same tribe as ragweed.
