Taxonomic name: Casuarina equisetifolia L.
Synonyms: Casuarina litorea L. var. litorea, Casuarina littorea Rumph
Common names: arbol de hierro (Spanish-Galapagos), Australian beefwood (English), Australian-pine (English), beach she-oak (English), beef wood-tree (English), bois de fer (French), casuarina, coast she-oak (English), Eisenholz (German), filao (French), horsetailtree (English), ironwood (English), pin d'Australie (French), pinheiro-da-Austrália (Portuguese), pino australiano (Puerto Rico), Strandkasuarine (German), whistling-pine (English)
Organism type: tree Casuarina equisetifolia is a deciduous tree with a pine-like appearance. The tree has been introduced for coastal landscaping but has become unpopular because of its invasive growth habit, aggressive choking of indigenous vegetation, and its interference with the nesting habits of turtles and crocodiles. It can produce tremendous numbers of small, winged seeds, which are dispersed by wind and water. It frequently colonises disturbed sites, is extremely resistant to salt spray and grows rapidly during hot weather. It does not do well in areas of prolonged flooding. Description
Swearingen (1997) describes C. equisetifolia, a member of the beefwood family (Casuarinaceae), as a deciduous tree with a soft, wispy, pine-like appearance that can grow to 30 metres or more in height. Also known as ironwood, beefwood, she oak, and horsetail tree, it bears a superficial resemblance to the conifer genus Pinus because of its small, round, cone-like fruits and its branchlets of scale-like leaves that look like pine needles. Its flowers are tiny and brown. The fruit is a nutlet a little more than a centimetre in diameter that contains winged seeds. Elfers (1988) reports that C. equisetifolia is monoecious. This is the tallest species of the genus in Florida (up to 40 m). Its drab, olive foliage is diffuse, primarily because of its widely spaced branches. Lateral branches originating low on stem often overtake the leader, producing a very broad, somewhat flat-topped, mature tree. The presence of hybrids is a cause of uncertainty in readily distinguishing this species at a distance. Similar Species
Casuarina cunninghamiana, Casuarina glauca
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Occurs in:
coastland, riparian zones, ruderal/disturbed Habitat description
C. equisetifolia occurs in open, coastal strand habitat, characterised by sand and shell beaches, rocky coasts, sand dunes, and sand bars in subtropical climates (Swearingen 1997). It frequently colonises disturbed sites, such as filled wetlands, road shoulders, cleared land, and vacant lots (Elfers 1988). Because its roots are capable of producing nitrogen through microbial associations, it can colonise nutrient-poor soils (Swearingen 1997). Rockwood et al. (UNDATED) report that C. equisetifolia prefers coarse-textured soils. It shows wide latitude in it's soil demands and ranges from dry, sandy beach ridges to wet lake margins, but it withstands inundation for short periods only. In southeastern Florida, the species is particularly prevalent on alkaline, lime stone-derived soils. It is tolerant of very saline conditions but grows best in slightly acid sandy soils. It reaches maximum development in slightly depressional topography where adequate moisture is nearly always available. Although it doesn't do well in areas of prolonged flooding, it is extremely resistant to salt spray and grows rapidly during hot weather (Elfers 1988). It is intolerant to cold (Snyder 1992). Casuarina species are reported to tolerate annual precipitation of 6.4 to 43 dm, annual temperatures of 22.1 to 26.9°C, and pH of 5.0 to 7.7 (Duke 1983). General impacts
Swearingen (1997) states that C. equisetifolia is fast-growing (1.5 to 3 metres per year), produces dense shade and a thick blanket of leaves and hard, pointed fruits, that completely cover the ground beneath it. Dense thickets displace native dune and beach vegetation, including mangroves and many other resident, beach-adapted species. 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 its leaves may inhibit the growth of other plants underneath it. The ground below the tree becomes ecologically sterile, reducing the food value for native wildlife. Unlike native shrubbery, the thick, shallow roots make it much more susceptible to blow-over during high wind events, leading to increased beach and dune erosion and interference with the nesting activities of sea turtles and American crocodiles. Elfers (1988) reports that Casuarina also poses a problem to humans because it is a source of respiratory irritation. Its pollen can cause allergic reactions symptomised by eye irritation, runny-nose, and hoarseness or sore throat. Uses
Elfers (1988) points out several minor uses that include the utilisation of wood ash in making soap and the extraction of dye from the bark. The astringent bark decoction is administered as a remedy for diarrhea and dysentery, as a lotion for beri-beri, and as a gargle to relieve sore throat. It is widely planted for amenity purposes, coastal reclamation, medicinal purposes, tannin, dyes, pulp and timber. Duke (1983) states that it is extensively cultivated for fuel, erosion control, and as a windbreak. The wood is used for beams, boat building, electric poles, fences, furniture, gates, house posts, mine props, oars, pavings, pilings, rafters, roofing shingles, tool handles, wagon wheels, and yokes. The needles have been employed in preparing active carbon by the zinc chloride method. Hill tribes of New Guinea use Casuarina in rotation to restore nitrogen to the soil. The most valuable use of C. equisetifolia appears to be as firewood, especially in third world countries (Elfers 1988). Notes
C. equisetifolia wood is very susceptible to drywood termites (Elfers 1988). Geographical range
Native range: Swearingen (1997) reports that C. equisetifolia is native to Malaysia, Southern Asia, and Oceania (islands of the Pacific between Asia and the Americas, including Australia).
Known introduced range: Hawai‘i, coastal Florida, Puerto Rico, the Bahamas, and many other Caribbean islands. C. equisetifolia is now one of the most common trees on frost-free beaches anywhere in the world (Duke 1983). Introduction pathways to new locations
Landscape/fauna "improvement": C. equisetifolia was introduced to Florida in the late 1800's and planted widely for the purposes of ditch and canal stabilization, shade, and lumber (Swearingen 1997).
People sharing resources: Elfers (1988) notes that seven Australian and one East Indian species of Casuarina were introduced into the United States before 1924, beginning with seeds brought from France in 1898 by the U.S. Dept. of Agriculture explorer, Dr. W. T. Swingle. Some seeds were distributed under erroneous names and problems of misidentification have continued since.
Local dispersal methods
On animals (local): The seeds have a membranous wing and are wind-dispersed (Binggeli 1997).
Water currents: The seeds can be water-dispersed (Binggeli 1997). Management information
Preventative measures: Whenever possible, efforts should be taken to prevent the introduction or encroachment of C. equisetifolia. For example, recently disturbed beach habitat may be planted with native vegetation to prevent C. equisetifolia from invading. A Risk Assessment of Casuarina equisetifolia for Hawai‘i and other Pacific islands was prepared by Dr. Curtis Daehler (UH Botany) with funding from the Kaulunani Urban Forestry Program and US Forest Service. The alien plant screening system is derived from Pheloung et al. (1999) with minor modifications for use in Pacific islands (Daehler et al. 2004). The result is a score of 15 and a recommendation of: "Likely to cause significant ecological or economic harm in Hawai‘i and on other Pacific Islands as determined by a high WRA score, which is based on published sources describing species biology and behaviour in Hawai‘i and/or other parts of the world." Physical: Impacts to native plants should be minimised during any control activities. The general consensus is that seedlings, saplings and young trees are best removed manually. Swearingen (1997) states that for new or small infestations, manual removal of seedlings and saplings is recommended. Fire is reported to be effective only in dense stands with sufficient dry fuel on the ground. Caution recommends follow-up treatments. Prescribed fire has been used for large infestations in fire-tolerant communities. Raking and removal of leaf litter, cones, and seeds should be done whenever possible. Chemical: For heavier infestations, application of a systemic type herbicide to bark, cut stumps, or foliage is likely to be the most effective management tool. An industry-wide survey instituted by the US Exotic Pest Plant Council of current eradication methods employed against Casuarina disclosed that a 2% mixture of Garlon 4 in diesel oil applied using the basal bark method or the hack-and-squirt method is most commonly used. Another herbicide frequently used is Garlon 3A by Dow. Biological: Casuarina has no natural enemies in its North American distribution and has a phenomenal growth rate that outpaces most other plants. Elfers (1988) summarises management research programs and notes that the lymantriid moth, Lymantria xylina, is one of the worst pests of C. equisetifolia in China. There has been a high rate of root rot in Florida Casuarina caused by the fungus Clitocybe tabescens. This has occurred primarily on higher, well-drained, light, sandy soils where oak and other hardwood trees were predominant before clearing. Stem canker and dieback attributable to the fungus Diplodia natalensis have affected trees in Puerto Rico. Ants have been a major source of control in both Puerto Rico and India, which probably explains why this tree has not over-run Puerto Rico. Nursery seedlings in India are attacked by: Brachytrupes achatinus (a cricket), Arbela tetraonis (a bark-eating caterpillar), Coelosterna scabrata (a longicorn), and the grubs of Oryctes rhinoceros (the rhinoceros beetle). Nutrition
C. equisetifolia can tolerate low soil fertility but is quite responsive to fertilisation with phosphorus or nitrogen and phosphorus (Rockwood et al. UNDATED). Reproduction
Elfers (1988) notes that C. equisetifolia produces thousands of wind borne seeds per plant and reproduces prodigiously following coppicing (cutting the stems from a stump, which produces more stems). It freely self seeds in disturbed areas, and seeds are dispersed by wind (Elfers 1988) and water (Binggeli 1997). A single 4- or 5-year-old tree can produce thousands of winged seeds that are carried by wind to new colonisation sites (Elfers 1988). Lifecycle stages
Elfers (1988) notes that seeds remain fertile for a few months to a year and germinate under conditions of adequate moisture and porous soil in 4-8 days. Young seedlings are extremely sensitive to drought, flood, and fire. Growth is most rapid during the first 7 years and then declines. Maximum growth is reached in 20 years with a maximum life span of 40 to 50 years. In Florida, growth rates have ranged from 0.5 -1.5 metres per year under stressed conditions and over 3 metres per year under cultivation. Reviewed by: Kenneth Langeland Professor, Extension Specialist, Agronomy. Center for Aquatic and Invasive Plants. Florida USA.
Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
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Last Modified: Thursday, 23 March 2006
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