Ambrosia ambrosioides (Franseria ambrosioides)
Common: Canyon ragweed, giant bur-sage
Family: Asteraceae
Origin: Southern Arizona and southern California, also in Baja California, Sonora, Sinaloa and Durango, Mexico. Habitat includes sandy washes and canyons, below 4,500 ft. elevation.
Temperature: Temperatures below 30 degrees F can be damaging, and this plant will freeze to the ground in the low 20s F. However, the plant usually recovers and looks lusher than before.
Light: Full sun or partial shade
Soil: Well drained soil
Water: Supplemental irrigation about every other week in summer keeps plants from looking ratty.
Better suited to supporting role. No exceptional features. Backdrop for flowering perennials or silver-leaved accent plants. Good to include in naturalistic wash planting. Shrubby perennial. Sunflower family. Usually woody at the base and sometimes throughout. Three feet high and 4 feet wide at typical mature size. Evergreen. Leaves are green above and below, hairy, elongated to lance-shaped, saw-toothed. 5" long and 1" wide. Branches are reddish brown with long white hairs. Flowers are yellowish green, to 3/8" wide, in terminal spike. Followed by clusters of cocklebur-like fruit with slender spines, about 1" long. Blooms February-May. Flowers are barely noticeable.
Twelve species of Ambrosia in Arizona. A similar species, Ambrosia trifida (Giant ragweed) is found in fields and along roadsides. Its abundant airborne pollen is dreaded by those who suffer with hay fever; if you have allergies, think twice about planting this ragweed relative.