Ambrosia dumosa is a common constituent of the creosote-bush scrub community throughout the Mojave desert of California, Nevada, and Utah and the Sonoran Desert of Arizona and northwestern Mexico (Baja California, Baja California Sur, Sonora, Chihuahua).
It is a form of ragweed, is a highly branched shrub 20 to 90 cm in height. The younger stems are covered with soft gray-white hairs. Approximately obovate leaves are 1 to 3 times pinnately compound or deeply lobed and generally clustered on short branches. The leaves are 0.5 to 4 cm long and also covered in soft gray-white hairs.
Its inflorescence is yellow with staminate and pistillate heads on a single plant (monoecious). Staminate heads have many flowers and are 3 to 5 mm in diameter with a 5 to 8 lobed involucre. Pistillate heads are 2 flowered and lack corollas.
Ambrosia dumosa becomes dormant during drought, losing all of its leaves to prevent water loss by transpiration; drought deciduous. During this time it can still be recognized by the presence of longitudinal stripes on smaller stems.
Like other types of Ambrosia this is a ragweed, wind blown pollen from burrobush can cause serious allergic reactions.