Name:
Pond apple
Botanical Name:
Annona glabra
Description
Pond Apple (Annona glabra) is a small tree usually growing 3 to 8 m tall, but occasionally reaching up to 15 m in height, that usually loses some of its leaves during the dry season (i.e. it is semi-deciduous). The trunks of younger trees have swollen bases and as the trees mature they may develop narrowly buttressed roots. The bark is usually light grey in colour and the branches bear numerous small raised projections (called lenticels).
The stalked leaves are simple and alternately arranged along the branches. They are oval in shape (7-15 cm long and up to 6 cm wide) and have a prominent midrib on their undersides. Fresh leaves are glossy on the upper surface and dull and paler green on the under surface, mostly hairless, and have pointed tips. The flowers (2-6 cm across) are pale yellow or cream in colour with a bright red centre. They have three large and leathery outer petals (25-30 mm long and 20-25 mm wide) and three smaller inner petals (20-25 mm long and 15-17 mm wide), as well as three broad sepals (about 4.5 mm long and 9 mm wide). Flowering occurs mostly during summer.
The fruit are very large (5-15 cm in size), somewhat round in shape, and initially green in colour. After the fruit are shed they turn yellow (when ripe) and then black (as they decay). These fruit have a pinkish-orange, rather dry, pungent smelling pulp that can contain more than 100 seeds. Each of the light brown coloured seeds is about 10-15 mm long.
For further information and assistance with identification of Pond Apple contact the herbarium in your state or territory.
Distribution:
This species is currently almost entirely distributed in the coastal districts of northern and central Queensland, mostly between Ingham and Cooktown but also south to Mackay and north to some of the Torres Strait islands. The vast majority of populations are present in the Cook pastoral district, but there are also a few records from the North Kennedy and South Kennedy pastoral districts, and a couple of recent naturalised records from the Moreton pastoral district. For example, more than 600 ha of the Russell River catchment, south of Cairns, are infested with Pond Apple. Pond Apple has the potential to spread throughout the estuaries and floodplains much of northern Australia. It is also known to be naturalised in tropical Asia and on several Pacific islands.
Habit:
Tree
Key points:
- Pond Apple (Annona glabra) is a small tree that was introduced into Australia as grafting stock for commercially grown custard apple.
- It has become an aggressive invader of freshwater and brackish wetlands, waterways, rainforests and coastal habitats in northern Queensland.
- It forms dense thickets that reduce biodiversity and threaten some rare species of flora and fauna.
- Pond Apple is difficult to manage because it often grows in sensitive areas that are hard, and sometimes dangerous, to access. Control methods must avoid adverse impacts on non-target plants or the surrounding environment.
- Dispersal agents such as feral pigs, Cassowaries and ocean currents also make it difficult to contain.
How it spreads:
Pond Apple reproduces by seed and may also produce suckers from damaged roots and trunks. The fruit and seeds both float and are commonly dispersed by water movement or during floods The hard seeds can remain viable for some time in fresh, brackish or sea water.
Ocean currents also play a major role in the distribution of Pond Apple along the coast, and the longshore flow carries seed washed out of river systems northwards up the coast. The seeds are also commonly spread by animals such as cassowaries and feral pigs. Research suggests that cassowaries can spread seeds 1-2 km, and that feral pigs can carry them as far as 10 km.
Where it grows:
Pond Apple prefers wetter tropical and sub-tropical habitats. It generally grows in freshwater and brackish swamps (e.g. in mangrove communities), in estuaries, along creeks and rivers, in rainforests and on rainforest margins, in coastal environs and along roadsides.. Some of the disturbed and undisturbed coastal ecosystems that Pond Apple invades include paperbark and pandanus wetlands, sedgelands, and high tide zones on beaches. It can withstand extensive flooding and trees can spend weeks at a time with their roots under water.
Flower colour:
Multi-colour
Distribution map:
Impacts:
Pond Apple is a Weed of National Significance (WONS). It is regarded as one of the worst weeds in Australia because of its invasiveness, potential for spread, and economic and environmental impacts.
Over time the dense thickets it forms can gradually replace everything else in the canopy and create an undesirable new habitat. Unlike many weeds, it can invade and transform undisturbed natural habitats. Its ability to grow in flooded areas and to tolerate salt water has enabled it to spread through much of northern Queensland’s wet tropics area. It now infests more than 2000 ha of the Wet Tropics Bioregion, and threatens melaleuca wetlands and native mangrove communities. Pond Apple is also a pioneering plant and will opportunistically invade areas after disturbances such as cyclones and floods.
While Pond Apple is mainly considered an environmental weed, its commercial impacts are also increasing as it spreads. It may also have impacts on the sugarcane and cattle industries in the future.
Origin:
Native to south-eastern parts of the United States (i.e. southern Florida), Mexico, Central America, the Caribbean, tropical South America and the coastal regions of tropical western Africa.
History:
Pond Apple was originally introduced to Australia as grafting stock for commercially grown custard apple in 1912 . It is still used commercially as a salt- and water-tolerant rootstock for custard apple in northern Queensland.
