Burrobush

Ambrosia dumosa or white bursage 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 headson 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 has spherical bur-like fruits ranging in color from golden to purple to brown. Along with microscopic hairs, the fruit has 12 to 35 flat and straight spines which are 5 to 9 mm in length and scattered over the surface. 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 burro-weed can cause serious allergic reactions. Increasing cases in Mojave Desert as the population grows from Joshua Tree, CA to Las Vegas, NV.