APC (2020). The Australian Plant Census, Council of Heads of Australasian Herbaria, Available at: Vascular Plants APC (biodiversity.org.au)
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Bitou Bush (Chrysanthemoides monilifera subsp. rotundata) is a perennial, evergreen, sprawling shrub which generally grows to 1-2 m in height, occasionally forming a canopy 10 m high. Its stems are branched and woody and the upper stems are often purple. The leaves, which are about 20-80 mm long, oval (symmetric, widest in the middle of the leaf) to oblong (length a few times greater than width, with sides almost parallel and ends rounded), to obovate (egg-shaped in outline with the widest part nearer the tip of the leaf) in shape, and the base attenuate (tapering uniformly at the base). Leaves arranged alternate along the stems. Unlike Boneseed, which has leaves with serrated edges (with teeth), Bitou Bush typically has leaves with smooth edges without teeth. Bitou Bush also has an extensive root system that makes it difficult to control. It does not produce a primary tap root. The decumbent stems (stems laying on ground with tips erect) can also produce roots at the nodes when those nodes are in contact with soil or moisture or become buried. Rooting of decumbent stems can lead to the formation of hummocks Winkler et al. (2008)
The inflorescence (flowers heads), are in groups of 3-12. Individual flower heads are up to 20 mm in diameter with each flower head possessing 5-8 fresh bright yellow petals around the edge and a deeper yellow centre, with peak flowering occurring from August to October. Each flower head is made up of many individual flowers crowded on to a receptacle at the end of the flower stalk. Flower heads are made up of two kinds of flowers, disc flowers (also known as tubular florets (or tubular flowers) in the centre that are the darker looking, and 5-13 ray (ligulate), flowers (ligules 8-10 mm long) around the edge are the flower head that appear to be individual petals, but are in fact individual 'ray' flowers.
The many small fruits are round drupes (like a fleshy berry) to 8-9 mm in diameter across obovoid (egg-shaped in outline with the widest part nearer the tip) to ellipsoid in shape, and have green fleshy skin that changes to black on maturity. The fruit contains a single egg-shaped seed 5-7 mm long which is dark brown to black when dry (CRC 2003). plants produce a prolific number of fruits with viable seed.
For further information and assistance with identification of Bitou Bush contact the herbarium in your state or territory.
Bitou Bush grows in a range of environments – from open exposed dunes to shaded forests. It is tolerant of shade, salinity, strong wind, windblown sand and water, drought, low nutrients and, to some extent, disturbances such as fire. It grows poorly in wet or swampy soils and has a low tolerance to frost (CRC 2003). Bitou bush occurs on a range of soil types but the majority of infestations are found on sandy or medium-textured, low fertility soils. It is unlikely to grow in constantly wet or inundated soils, however, it can grow on the edges of estuaries and mangroves, and damp margins of coastal dune ‘swale’ lakes and lagoons. It prefers disturbed areas, particularly near the sea, where it tolerates saline conditions. The optimal temperature for growth is between 17 and 27°C and plants have a low tolerance for frost (Howden 1984: In Winkler et al. 2008).
Bitou Bush can be confused with the closely related Boneseed (Chrysanthemoides monilifera subsp. monilifera). Boneseed differs from Bitou Bush by its upright growth habit (versus the sprawling habit of Bitou Bush), less rounded and more obviously toothed leaves, flowers with less petals (5-8 for Boneseed versus 11-13 for Bitou Bush) and round, smooth seeds (versus usually smaller and darker egg-shaped ribbed seeds for Bitou Bush). Bitou Bush is also mainly confined to coastal areas with summer rainfall whereas Boneseed is generally found in winter rainfall regions (Adair & Ainsworth 2000; Brougham et al. 2006).
Bitou Bush (Chrysanthemoides monilifera subsp. rotundata) is a Weed of National Significance and is regarded as one of the worst weeds in Australia because of its invasiveness, potential for spread, and economic and environmental impacts (CRC 2003). Without effective control programs, Bitou Bush has the potential to become more abundant within its current range and to spread into new areas.
Agriculture: Bitou Bush is not an agricultural weed and does not persist when grazed and trampled by stock, nor when land is cultivated.
Native ecosystems: Bitou Bush is an aggressive weed in coastal dune vegetation where it can out-compete, and in many cases totally eliminate, the native flora. The invasive success of Bitou Bush is due to its vigorous growth and prolific seed production. Bitou Bush grows faster than many native plants and is free of pests and diseases giving it a competitive advantage over natives. It forms a dense green thicket which can prevent native seedlings from growing. When it forms such dense stands, it can destroy, or drastically alter, the habitat of many native birds and animals as well (Winkler et al. 2008).
Bitou Bush forms dense shrub layers which can obscure entire sand dunes and change views of headlands and beaches. The most important impact of Bitou Bush is reduction of coastal biodiversity in infested areas. Bitou Bush affects a number of threatened species and plant communities, particularly in the Sydney region. Over 150 native plant species, three endangered plant populations and 24 ecological communities are under threat from Bitou Bush invasion in New South Wales alone.
There is evidence to suggest Bitou Bush invasion can result in the decline of some native bird populations. However, other bird species have been found to increase in abundance when Bitou Bush is present. Birds that forage almost exclusively on plant material, scavengers and raptors show lower abundances and species richness in weed-infested habitats (French & Zubovic 1997). A number of bat species and the Squirrel Glider are also suspected of being threatened by Bitou Bush invasion. However, the lack of research in this area makes this difficult to prove at this stage (Winkler et al. 2008).
Bitou Bush can also create a favourable environment for other highly invasive weeds, such as Asparagus Fern, Lantana and Glory Lily (CRC 2003). The higher soil nitrogen beneath the weed infestations could increase the competitive superiority of Bitou Bush directly by increasing growth rate, or indirectly by hampering the establishment of native species that are adapted to growing in nutrient-poor soils (Lindsay & French 2005).
It is difficult to determine an accurate estimate of the costs of environmental weeds. However, the cost of managing Bitou Bush in New South Wales alone in 2006/07, exceeded $4.3 million (Cherry 2008).
Urban areas: Not normally a weed of urban areas but may spread along coastal roadsides and occupy vacant areas of land where no grazing exists.
Bitou Bush spreads primarily by seed, with each plant producing up to 50 000 seeds a year. In established infestations, soil seedbanks can contain up to 5000 seeds per square metre. Soil disturbance (e.g. after bulldozing), fire and ingestion of seed by birds and other animals promote seed germination but seeds can still germinate in undisturbed situations.
Birds (such as Honeyeaters, Currawongs and Silvereyes) are important in spreading seed as they readily eat the fruit and then pass the seed, sometimes many kilometers from the original source. Rabbits and Foxes also eat the fruit and spread the seed in their droppings. Seeds are also spread by water, in ocean currents or through coastal creeks and waterways. Human activities can lead to the spread of Bitou Bush by vehicles and equipment. On a local scale, seeds may be spread in windblown sand. Bitou Bush can resprout after fire, slashing and herbicide application (CRC 2003; DEC 2006).
Bitou Bush was first recorded in Australia near Stockton (near Newcastle), New South Wales, about 1908. It was probably introduced through dumping of ships' ballast. From 1946 to 1968 it was planted along the coast by the New South Wales Soil Conservation Service to reduce dune erosion and revegetate areas after sandmining. It was also planted on sand dunes near Menindee in western New South Wales where a small infestation still persists (CRC 2003).
It is important to keep clean areas free of Bitou Bush (Chrysanthemoides monilifera subsp. rotundata). Once an infestation is established, preventing the spread of seeds into surrounding areas should be a priority. This means destroying established plants before they flower and produce fruit. Any Bitou Bush plants in gardens should be destroyed since they represent a seed source and hence potential for further spread (CRC 2003). Raising awareness amongst recreational vehicle users is important, particularly in coastal areas where seed may be spread by their activities (CRC 2003). In order to minimise the amount of seed produced, it is necessary to detect as many plants as possible. The greatest difficulty is the large area infested and the rapid re-invasion of an area after initial attempts at control. A sustained control effort is required for up to ten years. Where possible an integrated management approach should be adopted, using several control methods (CRC 2003).
Chemical control: Herbicides are effective against Bitou Bush and can be applied from the air, from the ground or by a cut and paint method (CRC 2003). Isolated plants can be treated with herbicide applied by spot spraying. In New South Wales low dosages of herbicides have been applied from helicopters in winter, allowing large areas to be treated rapidly with minimum impact on native species. Reports indicate better than 95% control (CRC 2003). The main four methods of herbicide application used are:
1. Cut-and-swab method where herbicide is applied to the stump of a felled plant.
2. Stem injection method where herbicide is injected in the sapwood of the plant in the main stem.
3. Foliar spray method where the leaves of the plant are sprayed with a herbicide solution.
4. Splatter gun application method where
However, other methods are available and Winkler et al. (2008) can be consulted for a .
NOTE: Training is normally a requirement in most States and Territories for all or some of the four methods.
Physical control: Because Bitou Bush has a shallow root system plants up to 1 m high can be easily pulled out.
Cultural: Bitou Bush does not persist when grazed or cultivated. However, slashing alone is not effective as plants will re-sprout from the stump unless herbicide is applied to the stems.
Fire: Fire can be effective in some areas as intense fires can kill mature Bitou Bush plants and may kill Bitou Bush seeds in the litter and topsoil while stimulating germination of seeds from lower in the soil profile. These seedlings must then be removed before flowering and producing further seeds. However, fire should not be used in areas where the remnant vegetation is known to be fire-sensitive. Fire can also cause other problems such as increased erosion potential, increased traffic and access by humans and pest animals, and further invasion by weeds (CRC 2003).
Biological control: Bitou Bush has also been recognised as a target for biological control through a cross-jurisdictional government process. This allows activities to be undertaken to develop effective biological controls. The first biological control agents for control of Bitou Bush and Boneseed were released in 1987. The Bitou Tip Moth (Comostolopsis germana) which destroys developing leaves, buds and flowers and reduces seed production and the Bitou Seed Fly (Mesoclanis polana), which destroys developing seed, have become well established (CRC 2003), in general biological control has had mixed success (Downey et al. 2007).
See CABI (2020); DPI NSW (2019); Winkler et al. (2008) for more detail on control methods.
YES. Nine agents released on C. monilifera with four establishing on bitou: bitou tip moth (Comostolopsis germana), bitou seed-fly (Mesoclanis polana), bitou leaf- roller moth (Tortrix sp.) and bitou tortoise beetle (Cassida sp. 3) (Harvey, et al 2023).
Seeds germinate at any time of the year but mostly in autumn and most seeds remain viable for at least two years. Althought germination occurs throughout the year, it more commonly occurs after favourable conditions such as rainfall or fire, as germination occurs most readily from weathered seeds. The seedlings grow rapidly during winter and a few plants may flower in the first year, particularly on burnt areas where there is little competition (Winkler et al. 2008).
On the south coast of New South Wales, seedlings usually reach flowering age after three years (earlier if growing in burnt or favourable conditions), while on the north coast growth is much more rapid and flowering within one year is more usual (CRC 2003). Bitou Bush can flower almost year round, but peak flowering occurs between April and June, unlike Boneseed which forms flowers in late winter and spring. Bitou Bush fruits ripen during winter and the start of spring (CRC 2003).
NSW, QLD, VIC, WA
Bitou Bush is naturalised in New South Wales and to a small extent in Queensland and Victoria. It is mainly restricted to coastal ecosystems with summer rainfall, similar to its range in South Africa.
A recent survey recorded Bitou Bush on 900 km, or 80%, of the New South Wales coastline, with an estimated 36 000 ha infested. Bitou Bush occurs almost continuously from the Shoalhaven River north to the Queensland border, with most of the north coast being heavily infested. Around Sydney there are mixed populations of Boneseed and Bitou Bush. National containment zones for Bitou Bush have been established in New South Wales on the far north coast and the south coast (CRC 2003; DEC 2006).
In Queensland, Bitou Bush occurred on coastal sand-mining areas from the New South Wales border to Hervey Bay and also on a number of offshore islands, including Fraser Island, Moreton Island and North Stradbroke Island. It has been targeted for eradication for the past decade and all plants are controlled each year. Smaller isolated infestations occur on Lord Howe Island and a few sites in Victoria (CRC 2003; DEC 2006). Bitou Bush may spread further into the understorey of forests and woodlands next to the coastal strip. Recent mapping has recorded infestations up to 50 km inland and it is able to spread inland along river edges.
In Western Australia several collections have been made from the same area in the Swan region, south of Perth
Both subspecies of Chrysanthemoides monilifera are native to South Africa. Boneseed (Chrysanthemoides monilifera. subsp. monilifera) is restricted to south-western South Africa where it is found on hilly terrain. Bitou Bush occurs in coastal vegetation extending from southern South Africa to southern Mozambique (Adair 1998).
Declared in all states and territories.
Chrysanthemoides monilifera subsp. rotundata