African rue (Peganum harmala)
Other common names
Wild rue, Rue weed, Syrian rue
African rue is a multi-branched and bushy perennial. A member of the Caltrop family, it is a succulent plant, with bright-green, alternating leaves that are smooth and finely divided with long, narrow segments. Plants grow 1.5 feet tall and three to four feet in diameter. Flowers are white, with five individual petals, and are present in spring to early fall. Fruit is located in a leathery capsule that is two- to four-celled and contains 45 to 60 seeds. Seeds are angular, dark brown and have a distinctive smell. When crushed, the stems have a disagreeable odor. The base of this plant is woody, and roots can branch and reach 20 feet in depth. African rue prefers distributed environments such as roadsides, fields and rangelands in desert and semi-desert areas. It is often found in soils with high salinity, and most parts of the plant contain allelopathic chemicals that reduce growth of other vegetation.
African rue contains at least four poisonous alkaloids. It is toxic to people and livestock. The seeds and fruit of the plant are the most toxic part, with a lethal dose being 0.15 percent of an animal's body weight. Young leaves are less toxic than seeds, with a lethal dose of about 1.0 percent of an animals's weight, while mature leaves are even less toxic. Dry leaves are apparently nontoxic. This noxious weed is extremely drought-tolerant and displays robust vegetative growth, expanding into desert rangelands and replacing native plants like saltbrush and grasses. It has a competitive advantage over native plants, as it germinates earlier in the spring.