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].
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].
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).
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. Find further fire regime information for the plant communities in which this species may occur by entering the species name in the FEIS home page under "Find FIRE REGIMES".
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].
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].
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]).
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].
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].
