Cestrum parqui_Mike Perlmutter
Photo by Mike Perlmutter

Cestrum parqui Risk Assessment

Common names: willow jessamine

Cestrum parqui -- California

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Evaluation Summary
Summary: 
General Evaluation Information
Date of Evaluation: 
May 18, 2016
Evaluation Time (hrs): 
2 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: 
A very widespread species that is most common in the south-eastern and eastern parts of Australia. It is very common in the coastal and sub-coastal regions of southern Queensland and eastern New South Wales. Relatively common in Victoria and central Queensland and scattered in south-eastern South Australia. Also collected near Perth in south-western Western Australia, but this may be from cultivated plants. Naturalised overseas in New Zealand and some parts of southern USA (i.e. California and Texas) (Weeds of Australia).
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: 
A very widespread species that is most common in the south-eastern and eastern parts of Australia. It is very common in the coastal and sub-coastal regions of southern Queensland and eastern New South Wales. Relatively common in Victoria and central Queensland and scattered in south-eastern South Australia. Also collected near Perth in south-western Western Australia, but this may be from cultivated plants. Naturalised overseas in New Zealand and some parts of southern USA (i.e. California and Texas) (Weeds of Australia). Overlaps with California climate zones, and is already present in CA (Cal-IPC).
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: 
Very High
Answer / Justification: 
This species is defined as a noxious plant in New South Wales under the Noxious Weeds Act, 1993 and all plants must be destroyed (EOL). Green cestrum (Cestrum parqui) is regarded as significant environmental weed in New South Wales and Queensland. It is currently listed as a priority environmental weed in three Natural Resource Management regions, and is also regarded as a sleeper weed in other parts of the country. In New South Wales it is of most concern on the north coast and in the wider Sydney and Blue Mountains region. In Queensland it is listed in the top 100 invasive plants in the south-eastern part of the state. It is also scattered in bushland around Adelaide and causing some concern in the warmer regions of Victoria (Weeds of Australia).
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: 
Very High
Answer / Justification: 
This species is defined as a noxious plant in New South Wales (Zones 7a-9b) under the Noxious Weeds Act, 1993 and all plants must be destroyed (EOL). Green cestrum (Cestrum parqui) is regarded as significant environmental weed in New South Wales and Queensland (8a-13b). It is currently listed as a priority environmental weed in three Natural Resource Management regions, and is also regarded as a sleeper weed in other parts of the country. In New South Wales it is of most concern on the north coast and in the wider Sydney and Blue Mountains region. In Queensland it is listed in the top 100 invasive plants in the south-eastern part of the state. It is also scattered in bushland around Adelaide and causing some concern in the warmer regions of Victoria (Weeds of Australia). Overlaps with California climate zones, and is already present in CA (Cal-IPC).
Reference(s): 
5. Are other species of the same genus (or closely related genera) invasive in a similar climate?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
Cestrum elegans is a weed in Victoria (Yarra Ranges Council). C. nocturnum is known to be invasive to many places including Hawaii, the Cook Islands, Fiji, French Polynesia, Western Samoa, Tonga, New Caledonia, and New Zealand (CABI). Many of these regions overlap with California climate zones (Cal-IPC).
Reference(s): 
6. Is the species (or cultivar or variety) found predominately in a climate matching the region of concern?
Yes or No: 
No
Points: 
0
Confidence Level: 
High
Answer / Justification: 
A weed of warmer temperate and sub-tropical regions that invades the margins of watercourses (i.e. riparian habitats) and is also found in parks, old gardens, waste areas, disturbed sites, open woodlands, forest margins, pastures and along roadsides (Weeds of Australia). Distributed globally: Argentina (Buenos Aires, Catamarca, Chaco, Cordoba, Corrientes, Entre Rios, Formosa Prov., Jujuy, La Rioja, Mendoza, Misiones, Rio Negro, Salta, Santiago del Estero, Santa Fe, San Juan, San Luis, Tucuman), Brazil (Rio Grande do Sul), Chile (Tarapaca, Antofagasta, Atacama, Coquimbo, Valparaiso, O'Higgins, Maule, Bio-Bio, Araucania, Los Lagos, Juan Fdz. Isl., Region Metropolitana), Paraguay (Cordillera, Presidente Hayes), Uruguay (Rocha, Tacuarembo), WC-Brazil (Mato Grosso do Sul), Bolivia (Chuquisaca, Cochabamba, La Paz, Potosí, Santa Cruz, Tarija), Juan Fdz. Isl. (introduced), Greece (introduced), Spain (introduced), Italy (introduced), Sicily (introduced), Australia (introduced) (SE-Queensland (introduced), E-New South Wales (introduced), Victoria (introduced), South Australia (introduced)), Pakistan (introduced), Java (introduced), Nepal (introduced), South Africa (introduced), Mozambique (introduced), tropical Africa (introduced), Madagascar (introduced), Kenya (introduced), USA (introduced) (California (introduced), Texas (introduced)), Madeira (introduced), Canary Isl. (introduced), Morocco (introduced), Tunisia (introduced) (GBIF). Grows best in USDA Hardiness Zones 8a-11 (Dave's Garden). Found in California counties: Amador, Contra Costa, Los Angeles, Marin, Napa, Orange, Santa Barbara, San Diego (CNPLX). The majority of the locations do not match the climate of California based on the Cal-IPC climate map (Cal-IPC).
Reference(s): 
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: 
Green cestrum (Cestrum parqui) grows vigorously and has been known to outcompete other vegetation on alluvial floodplains in Queensland. It has also formed reasonably dense infestations along degraded creek-banks and in overgrazed pastures. As it can form extensive stands along the edges of forests and waterways, it replaces indigenous plants in these habitats and prevents their regeneration (Weeds of Australia). On alluvial flats it has been known to outcompete most other vegetation (Global Invasive Species Database).
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: 
The plant does not create a fire hazard in natural ecosystems. Small or negligible effect on fire risk (Victorian Invasive Plants). Does not create a fire hazard (PIER).
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: 
This weed is considered a major problem because of its toxicity to livestock (especially cattle) and poultry which eat green cestrum when there is a shortage of other feed. All parts of the plant material, stems, leaves, berries and even partly burnt roots pose a serious threat to livestock. Death is usually rapid and painful. The plant is also known to be toxic to other livestock and humans (EOL). May cause death and hepatotoxicity in cattle (Cestrum parqui (green cestrum) poisoning in cattle). Green cestrum (Cestrum parqui) grows vigorously and has been known to outcompete other vegetation on alluvial floodplains in Queensland. It has also formed reasonably dense infestations along degraded creek-banks and in overgrazed pastures. As it can form extensive stands along the edges of forests and waterways, it replaces indigenous plants in these habitats and prevents their regeneration. The roots, stems, leaves and fruit of green cestrum (Cestrum parqui) are very toxic to livestock, domestic animals and humans, and stock losses have been reported (Weeds of Australia). Where it occurs in grazing land the value of the land would be affected (Victorian Invasive Plants).
Reference(s): 
10. Does the plant produce impenetrable thickets, blocking or slowing movement of animals, livestock, or humans?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
High
Answer / Justification: 
An upright (i.e. erect), much-branched, shrub usually growing 1-3 m tall, but occasionally reaching up to 5 m in height. It tends to form clumps and spread via suckers. Green cestrum (Cestrum parqui) grows vigorously and has been known to outcompete other vegetation on alluvial floodplains in Queensland. It has also formed reasonably dense infestations along degraded creek-banks and in overgrazed pastures. As it can form extensive stands along the edges of forests and waterways, it replaces indigenous plants in these habitats and prevents their regeneration (Weeds of Australia). An erect shrub 2 – 3 metres. It builds up large populations in moist habitats such as river flats, creekbanks and wetland edges. It has sometimes been planted as a hedge plant. High potential to block access to waterways. Due to its potential to build a large population in moist habitats, some associated recreational pursuits may be affected (e.g. swimming, boating, bird watching, etc) (Victorian Invasive Plants).
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: 
This plant reproduces mostly by seed, but also spreads vegetatively via root suckers. It tends to form clumps and spread via suckers (Weeds of Australia). Chilean cestrum reproduces from both creeping roots and seed (Agriculture Victoria). This species needs careful control because its extensive, shallow rooty system can produce many new plants from suckers, particularly after root disturbance or injury (Global Invasive Species Database).
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: 
No
Points: 
0
Confidence Level: 
Medium
Answer / Justification: 
It can also regenerate from root pieces that are dislodged during cultivation or roadside maintenance (Weeds of Australia). The literature cited states that root fragments can be detached by machinery, but this is not a mode of "natural detachment". It seems unlikely that this species disperses naturally by detached root fragments.
Reference(s): 
13. Does the species (or cultivar or variety) commonly produce viable seed?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
High
Answer / Justification: 
The plant grows vigorously, and it reproduces sexually and vegetatively (Victorian Invasive Plants).
Reference(s): 
14. Does this plant produce copious viable seeds each year (> 1000)?
Yes or No: 
Points: 
Confidence Level: 
Low
Answer / Justification: 
4+-1.5 seeds per fruit (Avian gut-passage effects on seed germination of shrubland species in Mediterranean central Chile). >2,000 assumed due to producing abundant berries containing seeds (Victorian Invasive Plants). Chilean cestrum can produce more than 2,000 seeds per plant with seeds remaining dormant in the soil for many years (Agriculture Victoria). Another source indicates that seed production is not more than 2000/sq-m (PIER). An exhaustive Google/Google Scholar search did not reveal any additional, conclusive evidence of this and it defaults it remains unanswered at this time.
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: 
High
Answer / Justification: 
Avian gut passage greatly enhances germination. 15.5% germinated when fruits were intact, 5% when seeds were manually extracted, and 95% when ingested and passed by the avian gut (Avian gut-passage effects on seed germination of shrubland species in Mediterranean central Chile). Seeds germinate in autumn (Victorian Invasive Plants). Seeds usually germinate in autumn but can remain dormant for years (Global Invasive Species Database). Without gut-passage, germination is relatively low (15%), but because birds are the most common seed dispersers for this plant, and germination is 95% after avian gut passage, it is likely that germination is quite high under natural conditions, and this warrants a "yes" answer.
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: 
Plants are at least 2 years old before flowering (Victorian Invasive Plants).
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: 
Very High
Answer / Justification: 
Flowering from late spring to autumn. These produce clusters of small, black egg shaped berries during summer to autumn (EOL). Flowers Jan - Sep (Avian gut-passage effects on seed germination of shrubland species in Mediterranean central Chile). Flowering occurs throughout the year, but is particularly abundant during spring (Weeds of Australia). Flowers July - Dec in California (Calflora).
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: 
Very High
Answer / Justification: 
Flowering from late spring to autumn. These produce clusters of small, black egg shaped berries during summer to autumn. Green cestrum is highly attractive to birds, and seedlings are often found growing under perching trees, along fence lines and on creek banks. It is also dispersed by water. Spread by birds, it invades gardens, rural lands and bushland (EOL). Birds are a major seed vector for this species (Avian gut-passage effects on seed germination of shrubland species in Mediterranean central Chile). The seeds are mostly dispersed by birds and other animals, but are sometimes also spread by water or in dumped garden waste (Weeds of Australia). Birds, water, pieces of root dragged by cultivation equipment (Victorian Invasive Plants). Water is an effective method of dispersal for this plant, as well as birds which eat the fruit and excrete viable seeds (Agriculture Victoria).
Reference(s): 
19. Are the plant’s propagules frequently dispersed long distance (>100 m) by wind or water?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Medium
Answer / Justification: 
Green cestrum is highly attractive to birds, and seedlings are often found growing under perching trees, along fence lines and on creek banks. It is also dispersed by water (EOL). The seeds are mostly dispersed by birds and other animals, but are sometimes also spread by water or in dumped garden waste (Weeds of Australia). Birds, water, pieces of root dragged by cultivation equipment (Victorian Invasive Plants). Water is an effective method of dispersal for this plant, as well as birds which eat the fruit and excrete viable seeds (Agriculture Victoria). It's growth near waterways and evidence of water dispersal warrant a "yes" answer.
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: 
No seed contamination (Victorian Invasive Plants). Birds, water, pieces of root dragged by cultivation equipment (Victorian Invasive Plants).
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: 
20
Number of questions answered: 
19
Screener Confidence (%): 
83.2
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Evaluation visibility: 
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