or Harmel [Peganum harmala L.][PEGHA][CDFA list: A] Photographs
Map of Distribution
SYNONYMS: harmel, Syrian rue, ruin
weed, rue, wild rue
DESCRIPTION: Bushy, herbaceous perennial
with short creeping roots, to 0.8 m tall. African rue contains
numerous alkaloids and all plant parts are toxic. Seed coats
contain the alkaloid harmine and are especially toxic when ingested. However,
livestock seldom consume plants because of the bitter taste. Toxicity symptoms
in guinea pigs include weakness and paralysis of the hindquarters. Dehulled
seeds yield edible oil similar to cottonseed oil. Plants have been used medicinally
and produce red dye in the Middle East. Introduced from the Mediterranean
region and Middle East.
SEEDLINGS: No description available.
PLANT: Stems stiff, erect, highly branched,
angled above, glabrous. Leaves alternate, fleshy, bright green, 2-5 cm long,
irregularly divided 3 times or more into linear segments. Stipules
and UNDERGROUND STRUCTURES: Taproot branched,
with stout, short-creeping lateral roots usually greater than 15 cm deep.
New shoots can develop from lateral roots.
FLOWERS: Late spring-early fall. Flowers white, ~ 2.5 cm in diameter
and solitary on stalks 2-5 cm long or more in the leaf axils. Sepals 5, linear,
~ 1.5 cm long. Petals 5, oblong, ~ 1.5 cm long.
and SEEDS: Capsules spherical, leathery,
7-15 mm in diameter, orange-brown at maturity, 3-chambered, and opening
by 3 valves at the apex to release numerous dark brown to black angular seeds,
3-4 mm long.
CHARACTERISTICS: Above ground parts die
back in winter.
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HABITAT: Dry places, such as roadsides and abandoned fields, in desert
and semi-desert regions. Grows best on sites that receive some run-off water.
DISTRIBUTION: Uncommon. Mojave Desert (cw San Bernardino, se Kern cos.).
PROPAGATION/PHENOLOGY: Reproduces primarily by seed, but roots can produce
new shoots, especially when severed. Most seed falls near the parent plant,
but some seed dispersed by water, human activities and machinery, or by adhering
to the feet, fur, or feathers of animals. Seeds can germinate under fairly
saline conditions. Germination starts in early spring and is sporadic throughout
the growing season when adequate moisture is available. Seedlings emerge from
soil depths to 3 cm, but most emergence occurs from the upper 0.5 cm.
FAVORING/DISCOURAGING SURVIVAL: Cultivation
can severe roots and encourage growth of new shoots.
SPECIES: African rue is the only
species in the genus Peganum occurring in California and is unlikely
to be confused with any other plants.
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Prevention and control:
African rue and Syrian bean-caper are both noxious perennial weeds in the
caltrop family and are native to the Mediterranean and central and southwest
Asia. Syrian bean-caper was believed to have been introduced to California
in 1931 as a contaminant in alfalfa seed from Turkestan. African rue was introduced
to the United States in 1931. These weeds are primarily problems in degraded
rangeland habitats or waste areas along roadsides. Both exhibit a bushy appearance
and die back to the crown each winter. New shoots arise from the crown or
lateral roots and extend in a radial fashion from the main taproot. Both species
are generally unpalatable to livestock and African rue has been reported to
be highly toxic to cattle, sheep, and horses.
Mechanical removal is a difficult task for either species. The strong, deep
taproot and lateral roots must be removed for control. Plants may be cut back
to the crown, but regrowth will occur. Tillage will only serve to spread infestations
by severing and dragging rootstocks to new areas. Longevity in the seed bank
for both species is unknown.
Grazing is not an effective control option, due to non-palatability or toxic
effects. There are also no available biocontrol agents for either species.
The most effective control strategy is a dilute spot application of glyphosate
to the foliage of actively growing plants in the bud stage. It will be necessary
to repeat this, possibly several times until the plants are completely killed.
Other nonselective herbicides such as tebuthiuron, diuron, and bromacil have
provided good roadside control. Triclopyr, 2,4-D, and dicamba may also be
effective, but no evidence has been reported in the literature. Refer to the
herbicide labels for rates and precautions.