Taxonomic name: Annona glabra L.
Common names: alligator apple (English), annone des marais (French), bullock's heart (English), cherimoyer (English), corossolier des marais (French), kaitambo (Fiji), kaitambu (Fiji), pond apple (English), uto ni bulumakau (Fiji), uto ni mbulumakau (Fiji)
Organism type: tree
Annona glabra is a highly invasive woody weed that threatens wetland and riparian ecosystems of wet tropics, world heritage areas and beyond. It can establish as a dense understorey that suppresses other growth leading to monocultures.
“Tree (2-) 3-8 (-12)m high, the trunk narrowly buttressed at the base; leaves oblong-elliptical, acute or shortly acuminate, 7-15cm long, up to 6cm broad; pedicel curved, expanded distally; sepals 4.5mm long, 9mm broad, apiculate; outer petals valvate, ovate-cordate, cream-coloured with a crimson spot at base within, 2.5-3cm long, 2-2.5cm broad; inner petals subimbricate, shortly clawed, 2-2.5cm long, 1.5-1.7cm broad, whitish outside, dark crimson within; stigmas sticky, deciduous; fruit up to 12cm long, 8cm broad, yellow outside when ripe, pulp pinkish-orange, rather dry, pungent-aromatic; seeds light brown, 1.5cm long, 1cm broad.” (Adams, 1972. In PIER, 2003)
riparian zones, ruderal/disturbed, wetlands
A semi-deciduous tree, usually 3-6m tall. Both the fruit and the seed float (an adaptation which facilitates dispersal in flowing water). The hard seeds can remain viable for considerable periods in either fresh, brackish or sea water. A. glabra can behave as a 'freshwater or brackish water mangrove' as it can survive root immersion at high tide and prolonged freshwater flooding. Seedlings require ample soil moisture and sunlight to survive. Such conditions can be expected on riverbanks and in naturally open wetlands or disturbed wetlands and rainforests.
In north Queensland, Australia, it forms dense monotypic stands which displace native vegetation, (PIER, 2003). Annona glabra is one of the worst invaders of the Wet Tropics. Its tolerance of salt and immersion in fresh water enables pond apple to invade melaleuca wetlands, where it forms a dense understorey and prevents young melaleucas from developing. (Wet Tropics Management Authority)
Naturalised and sometimes exhibiting invasive behaviour in French Polynesia, (PIER, 2003). In Australia excessive drainage of surrounding areas for land reclamation raises the saline water table level sufficient to kill melaleuca trees thus allowing invasion by the salt tolerant pond apple, (Land Protection, 2001).
Native range: Fresh and brackish wetlands in tropical North, Central and South America and coastal West Africa.
Known introduced range: Federated States of Micronesia (Pohnpei), Fiji, French Polynesia (Raiatea, Tahaa), Hawai‘i (Cult.). Australia, Viet Nam.
Introduction pathways to new locations
Agriculture: Introduced to Australia in 1912 as a grafting stock for custard apple. (Land Protection, 2001)
Local dispersal methods
Consumption/excretion: Fruit and seed spread by birds and animals. (PIER, 2003)
Water currents: The fruit floats and can survive prolonged immersion in fresh and salt water. (Land Protection, 2001)
Mechanical and chemical control measures can be effective but control is very site specific. Contact an expert for advice (Land Protection, 2001).
Physical: Pond apple trees and seed are readily destroyed by fire and research into the reintroduction of regular burning to areas that are tolerant to this practice, eg. sedge lands, may prove successful as a management tool, (Land Protection, 2001). Pulling and dozing has been successful in ditches and drains. (Land Protection, 2001)
Chemical: There are no chemicals currently registered for the control of pond apple although some herbicides are available for other woody weeds that grow in similar situations. Some trials involving overall spray, basal bark and stem injection have been conducted and this research is continuing. "Stems often fuse together giving the appearance of a single stem. In this situation each original stem maintains its own sap system. This complicates control by herbicide" (Land Protection, 2001).
From about two years old trees begin to flower and produce fruit, (Land Protection, 2001). Fruits and seeds spread by water, birds, and some mammals, (PIER, 2003). Each fruit contains up to 100 or more seeds about 1cm in length. Massive seed production has resulted in a 20cm deep carpet of seed covering the ground. (Land Protection, 2001)
Compiled by: IUCN/SSC Invasive Species Specialist Group (ISSG)
Last Modified: Thursday, 26 January 2006