Casuarina equisetifolia_Zoya Akulova
Photo by Zoya Akulova

Casuarina equisetifolia Risk Assessment

Common names: beach sheoak

Casuarina equisetifolia -- California

Primary tabs

Evaluation Summary
Summary: 
General Evaluation Information
Date of Evaluation: 
May 17, 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: 
AttachmentSize
PDF icon PRE_California_Matching_Results_1.pdf571.24 KB
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: 
Very High
Answer / Justification: 
The Australian pine has become naturalized in South Florida through self-seeding; was naturalized in the West Indies and Florida before 1920 (The Australian pine or beefwood (Casuarina equisetifolia L.) an invasive ‘‘weed’’tree in Florida; also see Ecology and management of Sheoak (Casuarina spp.), an invader of coastal Florida, USA).
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: 
Very High
Answer / Justification: 
The Australian pine has become naturalized in South Florida through self-seeding; was naturalized in the West Indies and Florida before 1920 (The Australian pine or beefwood (Casuarina equisetifolia L.) an invasive ‘‘weed’’ tree in Florida; also see Ecology and management of Sheoak (Casuarina spp.), an invader of coastal Florida, USA)). Florida is not a climatic overlap, but it does occur in climates which match California's in South Africa and Spain (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: 
Is a major economically and ecologically important invasive weed species in the United States, with expanding ranges in Hawaii and Florida (Invasive Plant Species). It was introduced and widely cultivated in Florida for coastal landscaping but has fallen into disfavor in the past 20 years because of its invasive growth habit and aggressive choking of indigenous vegetation (Barrett 1956). Casuarina equisetifolia is probably the most invasive species in south Florida (ELEMENT STEWARDSHIP ABSTRACT for Casuarina equisetifolia Australian Pine). It is reported to be invasive in a number of countries and is a particular problem in Florida and South Africa, and reportedly invasive elsewhere, e.g. Brazil and the Caribbean. Binggeli (1999) regards this species as highly invasive. It is classed as a category 1 pest plant on the Florida exotic pest plant council species list, meaning that it alters native plant communities (Miller et al. 2002). Henderson (2001) reports that it is listed as a category 2 invader in South Africa according to the Conservation of Agricultural Resources Act, 1983 where it is a potential 'transformer' of coastal dunes and sandy sea-shores. It is invasive along coasts in Puerto Rico, but is classed as a relatively low category of problem there (Federal Highway Administration, 2001); however, Francis and Liogier (1991) anticipate that while it is currently restricted to relatively small areas of Puerto Rican coasts and foothills it will eventually become common. Across the Caribbean it has also been reported invasive in Jamaica (IABIN, 2004), Dominican Republic (IABIN, 2003), Bahamas (Hammerton, 2001; BEST Commission, 2003). This species is classified as highly invasive by Binggelli (1999) (CABI).
Reference(s): 
Mullin, B. H., Anderson L. W. J., DiTomaso J. M., Eplee R. E., & Getsinger K. D. (2000).  Invasive Plant Species.
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: 
Is a major economically and ecologically important invasive weed species in the United States, with expanding ranges in Hawaii and Florida (Invasive Plant Species). It was introduced and widely cultivated in Florida for coastal landscaping but has fallen into disfavor in the past 20 years because of its invasive growth habit and aggressive choking of indigenous vegetation (Barrett 1956). Casuarina equisetifolia is probably the most invasive species in south Florida (ELEMENT STEWARDSHIP ABSTRACT for Casuarina equisetifolia Australian Pine). It is reported to be invasive in a number of countries and is a particular problem in Florida and South Africa, and reportedly invasive elsewhere, e.g. Brazil and the Caribbean. Binggeli (1999) regards this species as highly invasive. It is classed as a category 1 pest plant on the Florida exotic pest plant council species list, meaning that it alters native plant communities (Miller et al. 2002). Henderson (2001) reports that it is listed as a category 2 invader in South Africa according to the Conservation of Agricultural Resources Act, 1983 where it is a potential 'transformer' of coastal dunes and sandy sea-shores. It is invasive along coasts in Puerto Rico, but is classed as a relatively low category of problem there (Federal Highway Administration, 2001); however, Francis and Liogier (1991) anticipate that while it is currently restricted to relatively small areas of Puerto Rican coasts and foothills it will eventually become common. Across the Caribbean it has also been reported invasive in Jamaica (IABIN, 2004), Dominican Republic (IABIN, 2003), Bahamas (Hammerton, 2001; BEST Commission, 2003). This species is classified as highly invasive by Binggelli (1999) (CABI). The only area where it overlaps California's climate and is considered invasive is in South Africa (Cal-IPC).
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: 
No other species in the family extends farther beyond Australia than this. In its native range it is often the only tree present in the beach vegetation where it mainly occurs (ELEMENT STEWARDSHIP ABSTRACT for Casuarina equisetifolia Australian Pine). The Casuarina spp. are invasive plants in Florida that threaten biological diversity and beach integrity of coastal habitats. The trees include three species and their hybrids that aggressively invade riverine and coastal areas. Of the three species, C. equisetifolia and C. glauca are highly salt tolerant and widespread in coastal areas. The third species, C. cunninghamiana, invades riverine habitats (Ecology and management of Sheoak (Casuarina spp.), an invader of coastal Florida, USA). This area does not overlap with California's climate (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: 
Located in Alameda, Butte, Inyo, Los Angeles, San Bernardino, and San Diego counties in California. This species is distributed widely across the globe (GBIF), but most of the areas where it occurs do not match California's climate.
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: 
Very High
Answer / Justification: 
It was introduced and widely cultivated in Florida for coastal landscaping but has fallen into disfavor in the past 20 years because of its invasive growth habit and aggressive choking of indigenous vegetation (Barrett 1956). Once established, may inhibit the growth of native species. In 1980, Casuarinas numbered in the hundreds and thousands on several Florida Bay keys and on beaches from Cape Sable to the Ten Thousand Islands. Now one can expect to find pioneers on any sandy area above the high tide mark (Morton 1980). It is concluded from observation by experts that Casuarinas' inhibition of any undergrowth is the result of an aggressive and dense colonization habit and possibly to the production of phytotoxic exudations (Klukas 1969, Digiamberardino 1986, Okuda et al. 1982). In an experiment by Fernald and Barnett (1988), seedlings of indigenous species planted beneath a Casuarina canopy on spoil islands in the Indian River near Vero Beach, Fl. had a 54% survival rate. This implies that deterrents Casuarina presents to pioneers, whether physical, mechanical, or chemical, may be overcome or circumvented by introducing plants at the seedling stage. If phytotoxins are produced by Casuarina, they may only be inhibitory to germination. Even when Casuarina is planted along the highway there are rarely more than a dozen plant species growing below the canopy and the majority of these are other exotics (Austin 1978). A monotypic stand is a sterile system that harbors few native plants or animals (ELEMENT STEWARDSHIP ABSTRACT for Casuarina equisetifolia Australian Pine). Dense thickets of Australian pine displace native dune and beach vegetation, including mangroves and many other resident, beach-adapted species. Because its roots are capable of producing nitrogen through microbial associations, Australian pine can colonize nutrient-poor soils. Once established, it radically alters the light, temperature, and soil chemistry regimes of beach habitats, as it outcompetes and displaces native plant species and destroys habitat for native insects and other wildlife. Chemicals in the leaves of Australian pine may inhibit the growth of other plants underneath it (Fact Sheet: Australian Pine).
Reference(s): 
8. Is the plant noted as promoting fire and/or changing fire regimes?
Yes or No: 
No
Points: 
0
Confidence Level: 
Very High
Answer / Justification: 
Australian pine is very sensitive to fire, and may be killed by even a light burn (Floridata). May wildfire killed 60 to 70 percent of sheoak in Florida [10]. A smoldering controlled burn in Florida killed 90 percent of the sheoaks on the study plot [14]. A second attempt in the same area killed all the sheoaks; trunk diameters were between 5 and 8 inches (13-20 cm). Another tree, with a d.b.h. of 2 feet (0.66 m), was killed after charcoal was left to smolder at its base [14]. Trees less than 3 inches (8 cm) in diameter may sprout following fire.Trees larger than this usually die. Periodic fires coupled with the use of herbicides may be an effective method of controlling sheoak. However, too frequent, intense fires that kill overstory native pines may actually encourage Casuarina species to establish. Morton warns that burning Australian pine in peat soils may be hazardous. Elfer suggests that fire may be an effective control method for trees greater than 3 inches (8 cm) in diameter and in dense stands. Burning could be potentially harmful if the soil pH is changed such that native species cannot establish (USFS). An exhaustive Google/Google Scholar search did not reveal any additional evidence and this defaults to a “no” answer at this time.
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: 
While cattle readily eat the sprouts in Australia, they are recognized as high in tannin, astringent, and constipating, and are used for hardship fare only. It is now known that tannin interferes with digestive system utilization of protein, results in weight deficits, and is carcinogenic. Apart from the hazards that Casuarina presents to its habitat and to other plants and animals, it also poses a problem to humans because it is a source of respiratory irritation. Casuarina pollen can cause allergic reactions symptomized by eye irritation, runny-nose, and hoarseness or sore throat (Morton 1980) (ELEMENT STEWARDSHIP ABSTRACT for Casuarina equisetifolia Australian Pine). The pollen is plentifully airborne from December to April and has been definitely linked to respiratory complaints during these months (The Australian pine or beefwood (Casuarina equisetifolia L.) an invasive ‘‘weed’’tree in Florida). Australian pine tree’s dense shallow root system interferes with the ability of the endangered American crocodiles and sea turtles to construct coastal nests (Weed alert Australian pine (Casuarina species)). The alterations to ecosystems, direct and indirect negative impacts to wildlife, and substantial allergens to humans warrant a "yes".
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: 
Very High
Answer / Justification: 
Casuarina monocultures are usually flat without dune-swale topography and lack diversity in understory vegetation. The shallow root systems of the trees makes them susceptible to toppling during storms (Digiamberardino 1986). Reproduces prodigiously via coppicing to produce close, impenetrable stands. A monotypic stand is a sterile system that harbors few native plants or animals (ELEMENT STEWARDSHIP ABSTRACT for Casuarina equisetifolia Australian Pine). Dense thickets of Australian pine displace native dune and beach vegetation, including mangroves and many other resident, beach-adapted species. Because its roots are capable of producing nitrogen through microbial associations, Australian pine can colonize nutrient-poor soils. Once established, it radically alters the light, temperature, and soil chemistry regimes of beach habitats, as it outcompetes and displaces native plant species and destroys habitat for native insects and other wildlife. Chemicals in the leaves of Australian pine may inhibit the growth of other plants underneath it (Fact Sheet: Australian Pine).
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: 
When removed, control efforts must effectively kill the whole plant, including the roots, in order to prevent root suckering and growth from stumps. Reproduces prodigiously via coppicing to produce close, impenetrable stands (ELEMENT STEWARDSHIP ABSTRACT for Casuarina equisetifolia Australian Pine). Sheoak regenerates by seed as well as vegetatively through sprouting (USFS).
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: 
An exhaustive Google/Google Scholar search did not reveal any evidence and this defaults to a “no” answer at this time.
Reference(s): 
13. Does the species (or cultivar or variety) commonly produce viable seed?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
Freely selfseeds in disturbed areas (ELEMENT STEWARDSHIP ABSTRACT for Casuarina equisetifolia Australian Pine; USFS).
Reference(s): 
14. Does this plant produce copious viable seeds each year (> 1000)?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
Good seed crops occur annually (Schopmeyer 1974). A single 4 or 5 year old tree is able to produce thousands of seeds that are borne by winds to new colonization sites (Morton 1980) (ELEMENT STEWARDSHIP ABSTRACT for Casuarina equisetifolia Australian Pine). Australian pine is capable of flowering year- round and can produce tremendous numbers of small, winged seeds which are dispersed by wind (Fact Sheet: Australian Pine).
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: 
Seeds in a moist medium have germinated after exposure to light for 6 hours per day for 4 to 6 weeks. No pre-germination treatment is needed (Schopmeyer 1974). Seeds remain fertile for a few months to a year and germinate under conditions of adequate moisture and porous soil in 4-8 days (ELEMENT STEWARDSHIP ABSTRACT for Casuarina equisetifolia Australian Pine).
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: 
Very High
Answer / Justification: 
Minimum seed bearing age is 4-5 years, although there are reports of 1-2 years in stress environments. In the Everglades, C. equisetifolia (the only naturalized species in the U.S.) flowers twice a year beginning 3 to 5 years after germination (Morton 1980) (ELEMENT STEWARDSHIP ABSTRACT for Casuarina equisetifolia Australian Pine).
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: 
The peak of the flowering period appears to be April through June, with fruiting from September through December. In the Everglades, C. equisetifolia (the only naturalized species in the U.S.) flowers twice a year beginning 3 to 5 years after germination (Morton 1980). It flowers February through April and September through October, with fruits ripening in June and December (ELEMENT STEWARDSHIP ABSTRACT for Casuarina equisetifolia Australian Pine). Australian pine is capable of flowering year- round and can produce tremendous numbers of small, winged seeds which are dispersed by wind (Fact Sheet: Australian Pine).
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: 
Very few native songbirds find the Casuarina to be a resource of any value with the exception of migrating gold finches which feed on the seeds (ELEMENT STEWARDSHIP ABSTRACT for Casuarina equisetifolia Australian Pine). When ripe, the cones turn brown and the bracts on the cone open up, releasing small winged nuts. Birds including parrots and parakeets can disperse seeds (Anon., 2003). In Australia, the fruits of all species of Casuarina are a major food source for several species of parrot (Schodde et al., 1993). Referring to Casuarina species in general, Snyder (1992) states that seeds may be transported by animals (CABI).
19. Are the plant’s propagules frequently dispersed long distance (>100 m) by wind or water?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
It produces thousands of wind born seeds per plant (ELEMENT STEWARDSHIP ABSTRACT for Casuarina equisetifolia Australian Pine). Australian pine is capable of flowering year- round and can produce tremendous numbers of small, winged seeds which are dispersed by wind (Fact Sheet: Australian Pine). The cones are dispersed by water (Wild Singapore Factsheets). Primarily dispersed by wind (CABI).
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: 
No
Points: 
0
Confidence Level: 
Medium
Answer / Justification: 
An exhaustive Google/Google Scholar search did not reveal any evidence, there are no morphological adaptations for this kind of dispersal, and this defaults to a “no” answer at this time.
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: 
19
Number of questions answered: 
20
Screener Confidence (%): 
93.0
PRE Content Access and Privacy
Evaluation visibility: 
Public - accessible to all site users

Review this Evaluation

1280

Click on the button below to mark this evaluation as "Reviewed". Once you click the button, please wait a second, and the site will return to this Evaluation and your name will be on the "Reviewers List" in the right hand column (below the Evaluation Summary). For more information, please see the help page on How to Review an Evaluation?

Vertical Tabs