Peganum harmala_C253-03
Photo courtesy UC Davis Weeds of California

Peganum harmala Risk Assessment

Common names: African-rue

Peganum harmala -- California

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Evaluation Summary
Summary: 
General Evaluation Information
Date of Evaluation: 
August 31, 2016
Evaluation Time (hrs): 
3 Hours
Evaluation Status: 
Completed
Plant Information
Plant Material: 
If the plant is a cultivar, and if the cultivar's behavior differs from its parent's (behavior), explain how: 
Regional Information
Region Name: 
Climate Matching Map
These maps were built using a toolkit created in collaboration between GreenInfo Network, PlantRight, Cal-IPC, and Agricultural Sustainability Institute at UC Davis.
Climate Matching Maps PDF: 
Invasive History and Climate Matching
1. Has the species (or cultivar or variety, if applicable; applies to subsequent "species" questions) become naturalized where it is not native?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
High
Answer / Justification: 
Naturalized in California. Present in 2 counties according to Calflora. Also naturalized in Washington, Oregon, Nevada, Arizona, New Mexico, Texas, Australia and South Africa.
Reference(s): 
2. Is the species (or cultivar or variety) noted as being naturalized in the US or world in a similar climate?
Yes or No: 
Yes
Points: 
2
Confidence Level: 
High
Answer / Justification: 
Naturalized in California. Present in 2 counties according to Calflora. Also naturalized in Washington, Oregon, Nevada, Arizona, New Mexico, Texas, Australia and South Africa. It occurs in climates matching California in Washington, Oregon and Australia.
Reference(s): 
3. Is the species (or cultivar or variety) noted as being invasive in the U.S. or world?
Yes or No: 
Yes
Points: 
2
Confidence Level: 
High
Answer / Justification: 
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 (Oregon Department of Agriculture).
Reference(s): 
4. Is the species (or cultivar or variety) noted as being invasive in the US or world in a similar climate?
Yes or No: 
Yes
Points: 
3
Confidence Level: 
High
Answer / Justification: 
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 (Oregon Department of Agriculture). It occurs in climates matching California in Washington, Oregon and Australia.
Reference(s): 
5. Are other species of the same genus (or closely related genera) invasive in a similar climate?
Yes or No: 
No
Points: 
0
Confidence Level: 
High
Answer / Justification: 
Peganum is a genus with 5 species. The only one listed in Randall (2012) with invasive properties is P. harmala.
Reference(s): 
6. Is the species (or cultivar or variety) found predominately in a climate matching the region of concern?
Yes or No: 
Yes
Points: 
2
Confidence Level: 
High
Answer / Justification: 
P. harmala is found predominantly in climates which match California.
Impact on Native Plants and Animals
7. Does this plant displace native plants and dominate (overtop or smother) the plant community in areas where it has established?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
High
Answer / Justification: 
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 (Oregon Department of Agriculture). Most parts of the plant contain allelopathic chemicals that reduce the growth of surrounding native plants.
Reference(s): 
8. Is the plant noted as promoting fire and/or changing fire regimes?
Yes or No: 
No
Points: 
0
Confidence Level: 
Medium
Answer / Justification: 
P. harmala plants sprout after fire, but are not noted as promoting or changing fire regimes.
Reference(s): 
9. Is the plant a health risk to humans or animals/fish? Has the species been noted as impacting grazing systems?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
Reportedly poisonous to stock (Jepson eFlora). 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.
Reference(s): 
10. Does the plant produce impenetrable thickets, blocking or slowing movement of animals, livestock, or humans?
Yes or No: 
No
Points: 
0
Confidence Level: 
High
Answer / Justification: 
P. harmala is a perennial bushy herb that grows 1 to 1.5 feet tall and 3-4 feet in diameter. It is not tall or stiff enough to deter passage by humans or livestock.
Reference(s): 
Reproductive Strategies
11. Does this species (or cultivar or variety) reproduce and spread vegetatively?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
High
Answer / Justification: 
Local spread occurs when pieces of rootstock are severed and moved during cultivation (Parsons and Cuthbertson).
Reference(s): 
12. If naturally detached fragments from this plant are capable of producing new plants, is this a common method of reproduction for the plant?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
High
Answer / Justification: 
Reproduces by seed, but new shoots and plants are also produced from adventitious buds along lateral roots.
Reference(s): 
13. Does the species (or cultivar or variety) commonly produce viable seed?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Answer / Justification: 
Dissemination is primarily by seeds, the bulk of which fall close to the parent plant (Parsons and Cuthbertson).
Reference(s): 
14. Does this plant produce copious viable seeds each year (> 1000)?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
High
Answer / Justification: 
Reproduces by seed, but new shoots and plants are also produced from adventitious buds along lateral roots. Seed is secured in a leathery, fruit capsule; each plant may produce as many as 1,000 fruits. Each fruit has 45-60 seeds.
Reference(s): 
15. Is there significant germination (>25%) of seeds the next growing season, with no requirement of an infrequent environmental condition for seeds to germinate (i.e. fire) or long dormancy period?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
The heavy, unarmed seeds dispersed from dehiscent capsules of P. harmala do not exhibit dormancy, but germinate readily under favorable conditions of moisture and temperature (Abbott 2008).
Reference(s): 
16. Does this plant produce viable seed within the first three years (for an herbaceous species) to five years (for a woody species) after germination?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
High
Answer / Justification: 
Seeds germinate in early spring and flowering begins in late spring to early summer. Fruit ripens about 1 month after flowering stops (Parsons and Cuthbertson).
Reference(s): 
17. Does this plant continuously produce seed for >3 months each year or does seed production occur more than once a year?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
High
Answer / Justification: 
In southern New Mexico, plants die back to their roots during winter and initiate new annual growth in mid-to-late March. After spring growth and flowering, plants may become senescent (old-looking) and die back to the base as soils dry in summer. With cooler temperatures and additional moisture later in the season, African rue usually undergoes a second vegetative growth phase until freeze occurs in early November. In Australia, in established plants, flowering begins in spring with major peaks in November-December and the following March (Parsons and Cuthbert). In a study in northern New Mexico, flower production commenced at both sites in mid April, and fruit maturation occurred in June and July. Fruit maturation was related to calendar date and ambient temperature. In one population, senescent plants initiated new shoots in August and produced a second cohort of flowers (Abbot 2007).
Reference(s): 
Dispersal
18. Are the plant’s propagules frequently dispersed long distance (>100 m) by mammals or birds or via domestic animals?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
High
Answer / Justification: 
Dissemination is primarily by seeds, the bulk of which fall close to the parent plant, but some are moved in water flowing over the soil surface and in mud adhered to animals, farm machinery and other vehicles. Some may be spread by stock eating the plant and voiding the seed in their droppings. Local spread occurs when pieces of rootstock are severed and moved during cultivation (Parsons and Cuthbertson).
Reference(s): 
19. Are the plant’s propagules frequently dispersed long distance (>100 m) by wind or water?
Yes or No: 
No
Points: 
0
Confidence Level: 
Medium
Answer / Justification: 
Dissemination is primarily by seeds, the bulk of which fall close to the parent plant, but some are moved in water flowing over the soil surface and in mud adhered to animals, farm machinery and other vehicles (Parsons and Cuthbertson). According to the Oregon Noxious Weed profile there does not seem to be an adaptation to disperse a great distance via wind or water (no pappus, etc.). Sources indicate a leathery fruit, and drop near the parent plant. Deep in the text there is the statement: "Comments: Seeds have little potential for movement. Highly adapted to arid and semi-arid climates, may not thrive in wetter zones."
Reference(s): 
20. Are the plant’s propagules frequently dispersed via contaminated seed (agriculture or wildflower packets), equipment, vehicles, boats or clothing/shoes?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
High
Answer / Justification: 
Dissemination is primarily by seeds, the bulk of which fall close to the parent plant, but some are moved in water flowing over the soil surface and in mud adhered to animals, farm machinery and other vehicles. Some may be spread by stock eating the plant and voiding the seed in their droppings. Local spread occurs when pieces of rootstock are severed and moved during cultivation (Parsons and Cuthbertson).
Reference(s): 
Evaluation Notes
Total PRE Score

  • < 13 : accept (low risk of invasiveness)
  • 13 - 15 : evaluate further
  • > 15 : reject (high risk of invasiveness)

PRE Score: 
21
Number of questions answered: 
20
Screener Confidence (%): 
76.0
PRE Content Access and Privacy
Evaluation visibility: 
Public - accessible to all site users

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