Schefflera actinophylla



INTRODUCTORY


Photo © Forest & Kim Starr, Starr Environmental, Bugwood.org


AUTHORSHIP AND CITATION:
Gucker, Corey L. 2011. Schefflera actinophylla. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/ [].

FEIS ABBREVIATION:
SCHACT

NRCS PLANT CODE [53]:
SCAC2

COMMON NAMES:
octopus tree
Australian umbrella tree
umbrella tree

TAXONOMY:
The scientific name of octopus tree is Schefflera actinophylla (Endl.) Harms (Araliaceae) [27,56,62].

SYNONYMS:
Brassaia actinophylla Endl. [13]

LIFE FORM:
Tree


DISTRIBUTION AND OCCURRENCE

SPECIES: Schefflera actinophylla

GENERAL DISTRIBUTION:
Octopus tree is a nonnative species in central and southern Florida and all of the main Hawaiian islands. It is native to New Guinea and Queensland, Australia, but in Queensland, it is native only north of the Tropic of Capricorn [5,40,60]. Although octopus tree occurs at least as far north as Brevard and Pinellas counties in Florida [32], it is most common in southeastern Florida and the Florida Keys [28,37]. In Hawaii, octopus tree was first reported on the island of Molokai in 2000, but by this time, it was well known on Kauai, Oahu, Maui, and Hawaii islands [47]. Major octopus tree infestations occur in the Limahali Valley on Kauai and the Nuuanu and Waiahole Valleys on Oahu [46]. Plants Database provides a map of octopus tree's distribution.

In Florida and Hawaii, octopus tree was introduced as an ornamental on multiple occasions [21,56]. In Hawaii, octopus tree was also likely planted during reforestation efforts [59]. It was first introduced in Hawaii in 1900 [33] and in the contiguous states in 1927 [36]. Octopus tree was first reported outside of cultivation in Miami-Dade County in Florida (review by [3]). As of 1996, the Florida Exotic Pest Plant Council reported octopus tree in 28 designated natural areas that occurred in Monroe, Miami-Dade, Broward, Palm Beach, Brevard, Collier, and Pinellas counties [32]. As of 1997, octopus tree occurred in 44% of the preserves in southern Florida [6].

HABITAT TYPES AND PLANT COMMUNITIES:
Australia: In its native range of northern Queensland, octopus tree occurs in tropical lowland or monsoon rain forests [18,42]. In Queensland regions south of the Tropic of Capricorn, octopus tree has invaded undisturbed forests, remnant bushlands [40], melaleuca (Melaleuca quinquenervia) forested wetlands [63], and seashores dominated by coast banksia (Banksia integrifolia) [5].

Florida and Hawaii: In Florida and Hawaii, octopus tree has invaded undisturbed forests [37,46]. Octopus tree occurs in communities from cypress (Taxodium spp.) strands to sand pine (Pinus clausa) scrub and extreme habitats ranging from dry sand dunes to deeply shaded live oak (Quercus virginiana) hammocks [49]. In Miami-Dade County, octopus tree is especially invasive in undisturbed hardwood hammocks and to a lesser extent in pine rockland habitats ([37], Hammer 1996 personal communication cited in [32]). In Broward County, octopus tree occurred but with low importance and frequency in a laurel oak/cabbage palmetto (Q. laurifolia/Sabal palmetto) community [44]. Octopus tree may be epiphytic on laurel oak and cabbage palmetto [49]. In Hawaii, octopus tree is common on low-elevation, mesic, disturbed sites [56].


BOTANICAL AND ECOLOGICAL CHARACTERISTICS

SPECIES: Schefflera actinophylla
Photo © Forest & Kim Starr, Starr Environmental, Bugwood.org

Because very little primary literature and original research on octopus tree was available as of 2010, this summary has relied heavily on information presented in reviews, floras, horticultural references, fact sheets, and other gray literature [15,22,32,33,36,37,49]. Information presented in this literature often lacked supporting documentation and details, but several documents were written by land managers, botanists, or horticulturalists from invaded areas [15,22,32,49] and likely represent field observations. Additional research on octopus tree is necessary before much of the information in this and other documents can be properly assessed for accuracy and completeness.

GENERAL BOTANICAL CHARACTERISTICS:

Botanical description: This description covers characteristics that may be relevant to fire ecology and is not meant for identification. Keys for identification are available (e.g., [56,62]).

Octopus tree is a small, fast-growing evergreen tree with single or multiple bare trunks and few stout branches [32,33,46]. An octopus tree in Florida grew with a single main stem for many years, but once the stem was broken the tree produced 6 large trunks [36]. Trees may reach 40 feet (12 m) tall, and the irregular crowns may spread 15 feet (5 m) [15,56]. Trees can grow as epiphytes, especially when young [61]. Octopus tree produces very large, alternate, palmately compound leaves comprised of 5 to 18 droopy leaflets. The entire leaf, including leaf stalks and leaflets, can be 3 feet (0.9 m) long. The central leaflet is longest and may reach 12 inches (30 cm) long [33,56]. Head flowers that measure 1 inch (2.5 cm) across occur along stiff, crowded stalks that are 16 to 35 inches (40-90 cm) long and resemble octopus tentacles [32,33,56,62]. Flowers are typically restricted to trees in full sun conditions. Octopus tree produces clusters of fleshy drupes with 10 to 12 seeds [33,56]. In a tropical lowland rain forest in Queensland seeds averaged 2.7 mg when dry [18].

Raunkiaer [41] life form:
Phanerophyte

SEASONAL DEVELOPMENT:
Octopus tree flowers are possible from April through October in Hawaii [33] and in the summer or fall in Florida [61]. A single plant in Florida was observed for several years, and flowering was reported in March of one year, in August of another year, and occurred twice in another year [36]. Flowers in both summer and early fall were also reported by Austin (1996 as cited in [32]). Octopus tree flowers begin to develop into fruits after about 6 weeks or more [36].

REGENERATION PROCESSES:

Octopus tree reproduces by seed [33,36,37,39]. Vegetative reproduction and spread do not occur [43], although regeneration has occurred following trunk damage [36].

Pollination and breeding system: Octopus tree flowers are perfect [56] and contain nectar [9]. In Miami-Dade County, Florida, red-whiskered bulbuls, which escaped from captivity around 1960, regularly visit octopus tree flowers for nectar [11].

Seed production: Prolific seed production is reported for octopus tree ([21], Austin 1996 as cited in [32]). However, seed production is limited to sites in full sun [15,33] and does not occur until plants are 10 to 15 years old [33,36].

Seed dispersal: Fruit characteristics and field observations suggest that octopus tree seeds are primarily animal dispersed. Octopus tree fruits lack latex or other compounds that discourage herbivory [19]. In tropical lowland rain forests in Queensland, Australia, researchers report that octopus tree seeds are animal dispersed [18]. In New Guinea, some honey-eating bird species were observed taking octopus tree fruits from lowland tropical forests [9]. Bird and/or bat dispersal are reported for octopus tree seeds in Australia's Northern Territory [43], and in southern Queensland, bird dispersal is considered the predominant reason for octopus tree's invasion and spread in bushland habitats [40].

Common birds are responsible for some spread of octopus tree seed in Hawaii and Florida. Octopus tree fruits are a favorite of red-whiskered bulbuls, which were first recorded outside of captivity in Hawaii in 1965 [55]. In Florida, crows, mockingbirds, and starlings feed on octopus tree fruits and have transported seed into natural areas. Octopus tree abundance in natural areas on the Florida Atlantic University campus and in Boca Raton increased after starlings took over sparrow nests on the campus (Austin 1990 cited in [3]).

Seed banking: The literature available as of 2010 contained very little information regarding octopus tree seed banking. After reviewing storage records, experiments, and/or botanical expertise, researchers reported that octopus tree seed was viable in the soil for 6 months or more [43]. The frequency of octopus tree was 8.3% in mixed mesophyll rain forests in northern Queensland, where 1 seedling emerged from 12 soil samples [25].

Germination: No information available on this topic.

Seedling establishment and plant growth: Several sources report the presence of octopus tree seedlings [2,39], but the conditions for successful seed germination, seedling establishment, and survival were not reported in the literature available as of 2010. High population densities of octopus tree have been reported near seed sources [37], and seedlings in crevices of other trees with debris accumulations and available moisture have also been reported [33,36,39]. One researcher reports that when epiphytic roots reach the ground, octopus tree growth begins "in earnest" [36].

In its nonnative US habitats, octopus tree stands can be dense, near monocultures [21,37], but in monsoon rain forests in Australia's Northern Territory, most octopus tree populations consisted of 6 or fewer adults [43].

Vegetative regeneration: After extensive field observations and root excavations in monsoon rain forests in the Northern Territory, researchers concluded that octopus tree does not spread by clonal roots [43]. However, regeneration following stem breakage was observed. An octopus tree in Florida grew with a single trunk until it was broken in a hurricane. After this, the tree produced about 6 "massive" stems and developed into a spreading shade tree [36].

SITE CHARACTERISTICS:
In Hawaii, octopus tree occurs in mesic, disturbed and undisturbed habitats below 3,300 feet (1,000 m) [46,56]. In Florida, octopus tree is particularly invasive in wet, rocky areas in hammock habitats [31]. Growth of octopus tree is likely best on rich, moist soils in full sun [15].

Climate: Octopus tree is capable of establishing and spreading in tropical and warm-temperate climates [21]. In its native rain forest habitats of northern Queensland, average daily temperatures in the hottest months are 86 to 90 °F (30-32 °C) and in the coolest months are just 9 to 13 °F (5-7 °C) lower. Annual precipitation for 2 towns near the rain forest averaged 172 inches (4,382 mm) and 142 inches (3,609 mm). Ninety percent of the precipitation occurred over a 6-month period, and during this time, precipitation events of 20 inches (500 mm)/day were possible [25].

In the United States, octopus tree is generally restricted to areas where the average annual minimum temperature is above 30 °F (-1 °C) ([15], review by [32]). A few days of freezing temperatures are tolerated [33], and a horticultural reference reports that octopus tree grows where temperatures are generally above 18 °F (-8 °C) [36]. Octopus tree is moderately drought tolerant [15]. In southeastern Oahu, Hawaii, octopus tree occurred at the upper limit of the xerotropical region, near the Merriam moisture line, where annual precipitation averages 50 to 60 inches (1,270-1,520 mm), and precipitation and evaporation levels are nearly equal [13].

Soils: Octopus tree grows on slightly alkaline to acidic and occasionally wet to well-drained soils and is somewhat salt tolerant [15,33,37]. However, growth may be best on rich, moist soils [15]. In northern Australia, octopus tree occurred in wet/basic and wet/acidic monsoon rain forests. Its frequency was 70% in lowland spring areas with deep, humic, loamy soils over clay; 50% in forests with springs on sandstone slopes with deep sand colluvia; 40% in forests on deep, moist, surficial loams over sand; and 30% in lowland springs at floodplain or coastal margins on deep, organic, clay loams with water tables near the surface [42]. In northern Queensland, octopus tree occurred in mixed mesophyll vine rainforests on well-drained siliceous sands [25].

SUCCESSIONAL STATUS:
While successional studies were generally lacking, observations regarding octopus tree's tolerance of shade and disturbance suggest that it tolerates early-seral as well as late-seral conditions and may persist following disturbance.

Shade tolerance: Several US sources indicate that octopus tree is shade tolerant [40,46], though growth may be best in full sun [15]. It reportedly thrives within dense live oak canopies in Florida [49]. In its native rain forest habitats in Queensland, octopus tree was classified as a "light-demanding" species. However, "light-demanding" species were those establishing at forest edges or in single-tree or multiple-tree canopy gaps receiving 4% or more of full daylight photosynthetically active radiation under cloudy conditions [18].

Disturbance tolerance: Octopus tree has invaded disturbed and undisturbed sites in Florida and Hawaii [28,37,46,56,61]. Several sources report its survival and persistence following hurricane damage, and Little and Skolmen [33] indicate that pruning and topping are tolerated. Researchers suggested that octopus tree could spread "explosive(ly)" in areas damaged by Hurricane Andrew in south Florida [34]; however, reasons for this speculation were not given. On Chicken Key in Miami-Dade County, Florida, octopus tree was present in surveys conducted before and about 2 months after Hurricane Andrew [20]. Abundance was not reported. Another study reported high octopus tree survival after hurricane Andrew in Florida and hurricane Georges in Puerto Rico. About 85% of octopus trees were still standing after Andrew, which produced wind speeds of 265 km/hour. After Georges, which produced wind speeds of 177 km/hour in Puerto Rico, 87% of octopus trees were standing. Researchers calculated that if trees with more than 50% branch loss failed to survive, 79% of octopus trees would have survived hurricane Georges [12].


FIRE EFFECTS AND MANAGEMENT

SPECIES: Schefflera actinophylla

FIRE EFFECTS:

Immediate fire effect on plant: There were no studies (as of 2010) that described the immediate effects of fire on octopus tree. Limited anecdotal reports suggest that octopus tree may be killed by fire. Smith [46] claims that octopus tree is "destroyed" by fire, but provides no examples. Thayer [49], director of the Vegetation Management Division of South Florida, reports that "death by fire is no guarantee" for octopus tree: but again, reasons for this uncertainty are not given.

Postfire regeneration strategy [48]:
Unknown

Fire adaptations and plant response to fire: Fire studies in habitats invaded by octopus tree were not available as of the writing of this review (2010). Physiological and morphological characteristics suggest that octopus tree may not survive fire. Because reproduction and spread of octopus tree is limited to sexual reproduction [43], postfire sprouting is unlikely. However, sprouting following trunk damage or cutting has been reported [21,36]. Octopus trees have thin, bare trunks, which are probably poor insulators. Sometimes octopus tree develops surface roots or grows epiphytically [15,33]; surface and epiphytic roots would likely be killed or injured by fire.

Information about favorable conditions for octopus tree seed germination, seedling establishment, and growth is lacking, but populations have often been reported in disturbed areas [28,56,61]. Burned, open areas, therefore, may be potential establishment sites.

In southeastern Queensland, where octopus tree is considered invasive, it occurred on sites with evidence of past fire. Sites were thought to have burned with low to moderate frequency based on observations of blackened stems [63]. Time since the last fire was not reported.

FUELS AND FIRE REGIMES:
Octopus tree fuel characteristics and influences on fuel characteristics in invaded plant communities were not described in the available literature (2010). Altered fire regimes in habitats invaded by octopus tree were not reported. Fire studies in invaded habitats are needed.

See the Fire Regime Table for information on fire regimes in vegetation communities where octopus tree may occur.

FIRE MANAGEMENT CONSIDERATIONS:

Potential for postfire establishment and spread: Because octopus tree populations have been associated with disturbed sites [28,56,61], burned areas are potential habitat for seedling establishment and spread and should be monitored. Long-distance dispersal by birds suggests that postfire monitoring is advisable even in areas lacking a nearby seed source.

Preventing postfire establishment and spread: Preventing invasive plants from establishing in weed-free burned areas is the most effective and least costly management method. This may be accomplished through early detection and eradication, careful monitoring and follow-up, and limiting dispersal of invasive plant propagules into burned areas. General recommendations for preventing postfire establishment and spread of invasive plants include:

For more detailed information on these topics, see the following publications: [1,7,16,52].

Use of prescribed fire as a control agent: Because octopus tree may be killed by fire [46], prescribed fire in invaded areas may be useful for its management. As of 2010, however, the use of prescribed fire in controlling octopus tree was not reported.

Altered fuel characteristics: Octopus tree fuel characteristics and influences on fuel characteristics in invaded plant communities were not described in the available literature (2010).


MANAGEMENT CONSIDERATIONS

SPECIES: Schefflera actinophylla
FEDERAL LEGAL STATUS:
None

OTHER STATUS:
Information on state-level noxious weed status of plants in the United States is available at Plants Database.

IMPORTANCE TO WILDLIFE AND LIVESTOCK:
In Hawaii and Florida, octopus tree fruits are eaten by several bird species including, but likely not limited to, red-whiskered bulbuls, fish crows, mockingbirds, and European starlings ([55], Austin 1990 cited in [3]). Use of octopus tree foliage, fruits, and/or seeds by other animals was not reported in the United States as of 2010. However, in a controlled feeding study, octopus tree foliage was lethal to rats and mice (Quam and others cited in [49]).

Palatability and/or nutritional value: No information is available on this topic as of 2010.

Cover value: No information is available on this topic as of 2010.

IMPACTS AND CONTROL:

Impacts: Rapid growth, dense stands, and epiphytic forms make octopus tree potentially detrimental to native plant communities. Octopus tree can also damage pipes and housing foundations and cause contact dermatitis in sensitive individuals.

In Florida and Hawaii, octopus tree is a well-known invasive and often a control priority. The Florida Exotic Pest Plant Council classifies octopus tree as a Category 1 species in the central and southern portions of the state. Category 1 species are "invasive exotics that are altering native plant communities by displacing native species, changing community structures or ecological functions, or hybridizing with natives" [14]. In Hawaii, octopus tree is a "major pest" and in some forests may be the most common species [37]. Although growth and spread characteristics indicate that octopus tree may impact native plant communities and/or ecosystem processes, a search of published and unpublished information on octopus tree found no documentation of these impacts [17]. As of 2010, descriptions of octopus tree's impacts on native vegetation or community processes were mostly anecdotal.

Sources indicate that octopus tree is capable of rapid growth [15,46] and spread, which could negatively impact native plant communities. In 1982, octopus tree was reported as "rarely escaped" in Florida [60], but by 1996, it occurred in 28 designated natural areas in Monroe, Miami-Dade, Broward, Palm Beach, Brevard, Collier, and Pinellas counties [32]. High population densities have been reported near seed sources [37], and dense thickets likely reduce the amount of light, space, and nutrients available to native plants [21]. In endangered scrub habitats, octopus tree was shading out nodding pinweed (Lechea cernua), a threatened species in Florida (Austin and Burks personal observations cited in [32]). When growing as an epiphyte, octopus tree can "choke" and eventually kill host trees [36].

Octopus tree foliage can be toxic or physically irritating to some people [24,38], and root growth can damage housing foundations [40]. Foliage has caused dermatitis [38]. Skin lesions, fever, and painful joint swelling were reported for a child that handled octopus tree [24]. Consumption of octopus tree can cause burning in the lips, mouth, and throat, and airway swelling and closure may occur, but death from ingestion was not reported [49]. However, a controlled study found that rats fed pellets of 50% rat chow and 50% octopus tree foliage died from gastrointestinal hemorrhaging within 4 days of ingestion, and mice died within 7 days of ingestion (Quam and others cited in [49]).

Control: Octopus tree is reportedly difficult to control. Control of newly established, small, and/or young populations is probably easier than control of well established, mature populations. Land managers in Florida report that eradication of octopus trees with diameters greater than 10 inches (25 cm) is extremely difficult [31]. Bird dispersal of octopus tree seeds makes monitoring for new populations in and around control areas extremely important for successful management.

Control of biotic invasions is most effective when it employs a long-term, ecosystem-wide strategy rather than a tactical approach focused on battling individual invaders [35]. In all cases where invasive species are targeted for control, no matter what method is employed, the potential for other invasive species to fill their void must be considered [8].

Prevention: Although there has been widespread planting of octopus tree in Hawaii and Florida, eliminating future plantings could improve future control efforts. However, octopus tree remains a very popular landscape tree in tropical regions [37]. As of 2002, Florida nursery operators ranked octopus tree as one of the most valuable landscape plants [4]. When researchers surveyed nurseries in Florida, 10% of respondents indicated their nurseries grew or sold octopus tree. Average annual sales reported for octopus tree were $17,600, and the maximum annual sale reported was $384,000 [58].

It is commonly argued that the most cost-efficient and effective method of managing invasive species is to prevent their establishment and spread by maintaining "healthy" natural communities [35,45] (e.g., avoid road building in wildlands [51]) and by monitoring several times each year [26]. Managing to maintain the integrity of the native plant community and mitigate the factors enhancing ecosystem invasibility is likely to be more effective than managing solely to control the invader [23].

Weed prevention and control can be incorporated into many types of management plans, including those for logging and site preparation, grazing allotments, recreation management, research projects, road building and maintenance, and fire management [52]. See the Guide to noxious weed prevention practices [52] for specific guidelines in preventing the spread of weed seeds and propagules under different management conditions.

Fire: For information on the use of prescribed fire to control this species, see Fire Management Considerations.

Cultural control: Although not entirely serious, Thayer [49], director of the Vegetation Management Division of South Florida, suggests rumor mongering to improve control and discourage propagation of octopus tree. Thayer suggests that telling the public that octopus tree "attracts.......encephalitis-carrying mosquitoes" could limit its use in landscaping and potentially improve control.

Physical or mechanical control: Hand pulling of seedlings and young saplings has been recommended. Cutting of larger trees typically requires follow-up treatments to control sprouts [21].

Biological control: As of 2010, biological control of octopus tree was not reported. Biological control of invasive species has a long history that indicates many factors must be considered before using biological controls. Refer to these sources: [54,57] and the Weed control methods handbook [50] for background information and important considerations for developing and implementing biological control programs.

Chemical control: Octopus tree is very difficult to control with herbicides [49]. Effects of herbicide may not be seen for months, and follow-up treatments may be necessary. When octopus tree is growing as an epiphyte, herbicide applications require care to avoid harming the host plant [21]. Land managers with experience controlling octopus tree recommend cutting trees and treating the stumps with herbicide [31].

While herbicides are often effective in gaining initial control of a new invasion or a severe infestation, rarely are they a complete or long-term solution to weed management [10]. See the Weed control methods handbook [50] for considerations on the use of herbicides in natural areas and detailed information on specific chemicals.

Integrated management: No information is available on this topic.


APPENDIX: FIRE REGIME TABLE

SPECIES: Schefflera actinophylla
The following table provides fire regime information for habitats within octopus tree's distribution in Florida. Follow the links in the table for documents with more detail on these fire regimes.

Fire regime information on vegetation communities in which octopus tree may occur. This information is taken from the LANDFIRE Rapid Assessment Vegetation Models [30], which were developed by local experts using available literature, local data, and/or expert opinion. This table summarizes fire regime characteristics for each plant community listed. The PDF file linked from each plant community name describes the model and synthesizes the knowledge available on vegetation composition, structure, and dynamics in that community. Cells are blank where information is not available in the Rapid Assessment Vegetation Model.
Southeast
Southeast
Vegetation Community (Potential Natural Vegetation Group) Fire severity* Fire regime characteristics
Percent of fires Mean interval
(years)
Minimum interval
(years)
Maximum interval
(years)
Southeast Grassland
Everglades sawgrass Replacement 96% 3 2 15
Surface or low 4% 70    
Floodplain marsh Replacement 100% 4 3 30
Everglades (marl prairie) Replacement 45% 16 10 20
Mixed 55% 13 10  
Palmetto prairie Replacement 87% 2 1 4
Mixed 4% 40    
Surface or low 9% 20    
Pondcypress savanna Replacement 17% 120    
Mixed 27% 75    
Surface or low 57% 35    
Southeast Woodland
Longleaf pine (mesic uplands) Replacement 3% 110 40 200
Surface or low 97% 3 1 5
Longleaf pine-Sandhills prairie Replacement 3% 130 25 500
Surface or low 97% 4 1 10
Pine rocklands Mixed 1% 330    
Surface or low 99% 3 1 5
Pond pine Replacement 64% 7 5 500
Mixed 25% 18 8 150
Surface or low 10% 43 2 50
South Florida slash pine flatwoods Replacement 6% 50 50 90
Surface or low 94% 3 1 6
Southeast Forested
Sand pine scrub Replacement 90% 45 10 100
Mixed 10% 400 60  
Maritime forest Replacement 18% 40   500
Mixed 2% 310 100 500
Surface or low 80% 9 3 50
Mesic-dry flatwoods Replacement 3% 65 5 150
Surface or low 97% 2 1 8
South Florida coastal prairie-mangrove swamp Replacement 76% 25    
Mixed 24% 80    
*Fire Severities—
Replacement: Any fire that causes greater than 75% top removal of a vegetation-fuel type, resulting in general replacement of existing vegetation; may or may not cause a lethal effect on the plants.
Mixed: Any fire burning more than 5% of an area that does not qualify as a replacement, surface, or low-severity fire; includes mosaic and other fires that are intermediate in effects.
Surface or low: Any fire that causes less than 25% upper layer replacement and/or removal in a vegetation-fuel class but burns 5% or more of the area [22,29].

Schefflera actinophylla: REFERENCES


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