Quick Facts

Quick facts

• Pond Apple (Annona glabra) is a small tree that was introduced into Australia as grafting stock for commercially grown custard apple.
• It has since 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.

What Does It Look Like?

What is it?

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 (Navie 2007).

For further information and assistance with identification of Pond Apple contact the herbarium in your state or territory.

Flower colour

Multi-colour

Growth form (weed type/habit)

Tree

Where it currently grows? Preferred habitat

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 (Navie 2007). 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 (CRC 2003).

Are there similar species?

Pond Apple is easily confused with some native mangrove species because they look superficially similar and are often found growing together (CRC 2003). However, Pond Apple has quite distinctive cream and red flowers and very large rounded fruit during summer and autumn (Navie 2007).

Pond Apple is also similar to some closely-related introduced species that have also become naturalised in northern Queensland, including Bullock's Heart (Annona reticulata), Sugar Apple (Annona squamosa) and Soursop (Annona muricata). These species can be distinguished from Pond Apple by their fruit. Pond Apple fruits have relatively smooth shiny surfaces, while the fruits of these other species are either covered in short projections, or have rough or knobby surfaces (Navie 2007).

Why Is It A Weed?

What are its 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 (CRC 2003). Pond Apple is also a pioneering plant and will opportunistically invade areas after disturbances such as cyclones and floods (Land Protection 2006).

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 (CRC 2003).

How does it spread?

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 (Navie 2007). The hard seeds can remain viable for some time in fresh, brackish or sea water (CRC 2003). 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 (NHT 2004). The seeds are also commonly spread by animals such as cassowaries and feral pigs. Research suggests that cassowaries can spread seeds 1-2 km, whereas feral pigs can carry them as far as 10 km (CRC 2003).

What is its history in Australia?

Pond Apple was originally introduced to Australia as grafting stock for commercially grown custard apple in 1912 (Land Protection 2006). It is still used commercially as a salt and water tolerant rootstock for custard apple in northern Queensland (CRC 2003).

How To Manage It?

Best practice management

Pond Apple usually grows in sensitive areas so control methods should be chosen that do not have an adverse impact on non-target plants or on the surrounding environment. 

Chemical control: Herbicides recommended to control Pond Apple are available at present through permit for 'minor off-label use'. Stem injection and cut stump are the preferred method for treating Pond Apple in aquatic habitats because it minimises herbicidal runoff and impacts on non-target plants and animals. In still, dry conditions, herbicide can also be applied by basal bark spraying and foliar spraying of seedlings (CRC 2003).

Non-chemical control: Pond Apple can also be controlled mechanically by hand pulling, chain pulling and dozer pushing. Chain pulling and dozer pushing are only suitable on flat country in areas free of sensitive vegetation, where machines can manoeuvre easily (Land Protection 2006). Such sites must be monitored for new seedlings and should be revegetated with native plants (CRC 2003). Pond Apple is also very susceptible to fire; however, sufficient fuel is not often available in dense infestations of this species (Land Protection 2006). 

Biological control: This is currently not an option, mainly because other closely-related species are grown commercially in Australia (CRC 2003).

Check with your local council or state/territory government agency about its requirements for Pond Apple control. Also see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au .

For further information on control methods see the Pond Apple manual (available at https://www.weeds.org.au/WoNS/pondapple/ )

Does it have a biological control agent?

NO

When does it grow? (lifecycle/growth calendar)

Pond Apple plants start reproducing after two years in the tropical regions of northern Australia. The flowers are produced during summer, do not self-pollinate and pollination is probably brought about by beetles. The fruit form over summer and autumn and drop from the tree after only a short time. The fruit matures after being dropped, the skin turning from green to yellow to black while the flesh turns orange. Leaves of mature trees turn yellow and fall in the dry season. Germination peaks after rainfall and requires a period of temperatures above 25 ºC (CRC 2003).

Where Is It Found?

Which states and territories is it found?

QLD

What areas within states and territories is it found?

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 (CRC 2003). 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 there are several recent naturalised records from the Moreton pastoral district (Bostock and Holland 2007). 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 (CRC 2003). It is also known to be naturalised in tropical Asia and on several Pacific islands (PIER 2006).

Where does it originate?

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 (GRIN 2007).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

YES

Where is it a declared weed?

Declared in all states and territories

Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?

NO

Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?

NO

Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Annona glabra

Other scientific names (synonyms)?

Does it have other known common name(s)?

Pond-apple Tree, Alligator Apple, Bullock's Heart, Cherimoya, Monkey Apple, Bobwood, Corkwood