African Rue (Peganum harmala)
African rue is a multi-branched and bushy perennial 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 3-4 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 2-4 celled that contains 45-60 seeds. Seeds are angular, dark brown and have a distinctive smell. When crushed, the stems also have a disagreeable odor. The base of this plant is woody and roots can branch and reach 20 feet in depth. African rue prefers disturbed 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.
Height of mature plants
It can bloom from April through November.
African rue primarily grows in deserts.
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 then seeds with a lethal dose of about 1.0 percent of the animal’s weight, while mature leaves are less toxic. Dry
leaves are apparently nontoxic. This noxious weed is extremely drought tolerant and displays robust vegetative growth expanding into desert rangelands replacing native plants like salt brush and grasses. It has a competitive advantage over native plants as it germinates earlier in the spring.
Weed Seed: Peganum harmala (African-rue)
Prohibited Noxious, Class 1 in the Canadian Weed Seeds Order, 2016 under the Seeds Act. All imported and domestic seed must be free of Prohibited Noxious weed seeds.
Canadian: Absent from Canada (Brouillet et al. 2016 Footnote 1 ).
Worldwide: Native to desert regions of northern Africa, Asia, and southern and eastern Europe. Introduced to the United States, where it is found across the southwest and Pacific states. Populations are currently concentrated in Arizona, New Mexico and Texas (CFIA 2012 Footnote 2 ).
Duration of life cycle
Seed or fruit type
- Seed length: 2.0 – 4.5 mm
- Seed width: 1.5 – 3.0 mm
- Trigonous seed; shaped similar to an orange wedge
- Seed surface is rough, bubbled and/or covered with reticulations
- Edges of the seed are winged
- Seed is blackish-red to red, translucent
- Hilum is a small hole at one end.
Habitat and crop association
Occurs mainly in dry grasslands and saline waste areas, but also common along roadsides, field edges and in degraded pastures. Prefers disturbed environments (CFIA 2012 Footnote 2 ).
African-rue has long been used as a dye plant and was imported into New Mexico in 1928 for “Turkish Red” dye (Guclu and Ozbek 2007 Footnote 3 ). It has since spread into Texas and Arizona and along the western coast of the United States (Abbott et al. 2007 Footnote 4 ).
Natural spread is mostly by seed, and occurs by water moving over soil or by animals that deposit the seeds in their droppings. Humans also plant this species for medicinal purposes and spread it unintentionally by moving pieces of rootstock with vehicles or machinery (CFIA 2014 Footnote 5 ). African-rue contains alkaloids that are toxic to grazers, including horses, sheep and cattle.
No similar species
African-rue (Peganum harmala) seeds African-rue (Peganum harmala) seed African-rue (Peganum harmala) seed, hilum view African-rue (Peganum harmala) capsule
Brouillet, L., Coursol, F., Favreau, M. and Anions, M. 2016. VASCAN, the database vascular plants of Canada, http://data.canadensys.net/vascan/ [2016, May 30].
Guclu, C. and Ozbek, H. 2007. Biology and damage of Thamnurgus pegani Eggers (Coleoptera: scolytidae) feeding on Peganum harmala L. in eastern Turkey. Proceedings of the Entomological Society of Washington 109: 350-358.
Abbott, L. B., Lepar, D. and Daniel, D. L. 2007. Vegetative and reproductive phenology of African rue (Peganum harmala) in the northern Chihuahuan Desert. The Southwestern Naturalist 52 (2): 209-218.
African rue was introduced to the United States and has become a noxious weed. It smells foul when crushed. It is a much-branched perennial whose basal woody stems persist though upper foliage dies back each year. It grows to a height of 2-3 feet. The leaves are pinnatifid with linear, smooth segments. There are four or five white petals that have greenish veins and 8-10 stamens with filaments that are dilated at the base. The fruit is a globular capsule that contains many seeds. African rue is found in dry waste areas.
This weed is extremely toxic to cattle, sheep, horses, and humans; it contains at least four poisonous alkaloids. The seeds and fruit are the most toxic, followed by young leaves and mature leaves. Animals typically avoid eating African rue because of its bad taste and smell. Most parts of the plant contain allelopathic chemicals that reduce the growth of surrounding native plants.
Scientific Name Peganum harmala Plant Type Forb Growing Season Warm Season Stem Placement Alternate Habitat Wastelands Flower Color White
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