Introduced from Europe as a desirable ornamental shade tree and source of food for wildlife. Now found throughout the U.S. except for the southeast states, and listed as a noxious and invasive weed species in many states.
An evergreen perennial tree that reproduces from its seeds, and production of fruit and seeds can be extensive. While it is grown as an ornamental it also easily invades natural areas, particularly along waterways, and becomes a serious problem.
Mature trees grow to 35 feet in height and are widely sprawling to over 20 feet across, with branches and foliage covering the soil below. The trunk and branches are lined with spines up to 2 inches in length. Leaves are narrow and to about 3 inches in length, covered on both surfaces with minute scales that give the leaf a powdery gray appearance. Flowers are minute and yellow, but arranged in long, dense clusters. The fruit is an olive about ¾ inch long and brownish when mature, forming on a short stalk along the stems between the leaves.
Characteristicts Important to Control:
Mature trees can be killed with a systemic herbicide, but would need to be removed physically as well. Pre-emergents may be only mildly successful against the prolific seed production, and continued applications of a contact herbicide may be needed as new seedlings emerge.