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Limnocharis flava

Description
 

Yellow Burrhead (Limnocharis flava) is an erect, clump-forming, aquatic herb to about 1 m high that grows rooted in the mud and emerges above the water surface when standing in water. It is perennial where moisture is present all year-round, but annual in ephemeral waterbodies and sites with pronounced dry seasons (van Steenis 1954; Haynes & Holm-Nielsen 1986; Sainty & Associates 2002; CRC 2003; GISD 2005; Johnson & Osmond undated; Weeds Australia undated).

The large leaves arise in clusters from a short, stout rhizome (to 3 cm long). The thick, bright green leaf blade is broadly ovate to elliptic, with a rounded to abruptly pointed tip, 5-30 cm long and 3-25 cm wide. It usually has 11-15 longitudinal veins and numerous finer transverse veins between them. The leaf stalk (petiole) is thick, fleshy, and triangular in cross-section, 5-90 cm long.

The flower head sits on a flowering stalk about as long as the leaves. The flower head (inflorescence) consists of a cluster (umbel) of 2-15 flowers, each on a short stalk 3-7 cm long. The cup-shaped flowers are 2-4 cm across, with an outer whorl of 3 green perianth parts and with an inner whorl of 3 'petals' 1.5-3 cm long and yellow with the centre darker and the outer part of the 'petals' paler to almost white. There are more than 15 stamens in each flower.

The fruits are more or less spherical capsules 1.5-2 cm in diameter that split into crescent-shaped segments, each containing numerous brown, horseshoe-shaped seeds to 1.5 mm long with distinct ridges. When fruiting, the flowering stalk bends towards the water and may bury the fruit in mud or water (to release and disperse the fruit and seeds). New plants (ramets) may develop from the flower head vegetatively (van Steenis 1954; Haynes & Holm-Nielsen 1986; Sainty & Associates 2002; CRC 2003; GISD 2005; Johnson & Osmond undated; Weeds Australia undated).

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

Distribution:

Yellow Burrhead is naturalised in north-eastern Queensland: in the Cairns area, and near Feluga, Mossman and Townsville (Department of Natural Resources & Mines 2005). Although known infestations occupy an area of less than 3 ha, other plants of Yellow Burrhead are likely to occur in suburban gardens and there may be undiscovered naturalised populations (Waterhouse 2003).

Habit:

Herb, Aquatic

Key points:
  • Yellow Burrhead (Limnocharis flava) is an aquatic herb to about 1 m tall with rather succulent triangular leaf and flower stalks, rounded leaf blades and a loose umbellate cluster of pale yellow flowers with 3 'petals'.
  • It is a prolific seed-producer with tiny seeds dispersed by water and other agents.
  • It also spreads vegetatively and rapidly under favourable conditions such as high nutrient levels.
  • Some cultivated plants and several small, naturalised populations were found in the Cairns and Townsville districts of north Queensland in 2001/2002.
  • If unchecked, Yellow Burrhead could become a very invasive environmental weed of wetlands and streams, particularly in humid tropical regions of northern Australia.
How it spreads:

Yellow Burrhead reproduces quickly, both by seed and vegetatively.

It is a prolific seed-producer and the seed may persist for many years (Sainty & Associates 2002). A single fruit produces about 1 000 seeds and a single plant may produce as many as one million seeds per year (Kotalawala 1976). Mature fruits and individual segments can float for several days, scattering seeds as they float downstream. Seeds may also be carried in mud sticking to the feet of birds, on people's shoes and clothing, or agricultural and other equipment (Kotalawala 1976; GISD 2005).

Vegetative plantlets (daughter plants called ramets) develop from the central inflorescence bud (after the flowering stem loses its flowers and bends over towards the mud). They either root in the mud or break off and float away to form new infestations (CRC 2003; Waterhouse 2003; GISD 2005; Johnson & Osmond undated).

Yellow Burrhead has been spread to many parts of the world by humans as an ornamental plant for aquaria and ponds, and as a food source (GISD 2005).

Where it grows:

Yellow Burrhead usually grows partly immersed in water, preferring shallow, stagnant or slow-flowing water. It grows in tropical to subtropical conditions, in freshwater pools, swamps, wetlands, ditches and at the edges of deeper waterbodies such as streams and dams. It thrives in nutrient-enriched water (Johnson & Osmond undated).

Flower colour:Yellow
Distribution map:

Australia's Virtual Herbarium at http://www.anbg.gov.au/cgi-bin/avh.cgi 

http://www.weeds.org.au/cgi-bin/weedident.cgi?tpl=plant.tpl&ibra=all&card=W09 

Impacts:

Yellow Burrhead is an aquatic plant that could become a major weed of wetlands, slow-moving streams and dams in tropical and semi-tropical areas (CRC 2003; Johnson & Osmond undated).

 

It is a threat to the environmental integrity of wetlands, as this weed competes with native plants for space, light and nutrients. The altered ecological balance may then seriously impact on native aquatic fauna (Department of Natural Resources & Mines 2005). Clumps of the weed provide suitable breeding sites for disease-carrying mosquitoes (GISD 2005).

 

Yellow Burrhead also chokes and reduces the effectiveness of irrigation and drainage channels, blocking or slowing water flow and trapping silt and other sediments. This can interfere with flood mitigation (Sainty & Associates 2002; Department of Natural Resources & Mines 2005; Johnson & Osmond undated).

 

Yellow Burrhead is a serious agricultural and economic weed overseas. In south and south-east Asia, it is a major weed of rice paddy fields (Kotalawala 1976; Sainty & Associates 2002; Karthigeyan et al. 2004; Department of Natural Resources & Mines 2005).

Origin:

The genus Limnocharis includes two species, native to the Americas. Yellow Burrhead is native to tropical America, from Mexico to Paraguay and to the Caribbean Islands (Sainty & Associates 2002). For distribution details see GISD (2005) and GRIN (undated).

History:

Yellow Burrhead has become a pest of rice fields and a serious environmental weed from India throughout South-east Asia to Indonesia, and in the United States (CRC 2003). It has been introduced and spread by humans as an ornamental plant for ponds and water gardens, possibly as a seed contaminant in rice and other agricultural imports, and as a source of food; the leaves being used in many countries as a vegetable, sometimes with the popular belief the plant has medicinal properties. It is also used as animal fodder (Kotalawala 1976; GISD 2005).

The first record of Yellow Burrhead in Australia was of several cultivated plants, found in 2001 in an ornamental pond near Cairns in north Queensland. The source was a naturalised population in a freshwater lake in the Cairns area. This infestation was controlled and the area monitored for re-infestation. Publicity about Yellow Burrhead's potential weed status revealed further infestations in the Cairns and Townsville districts (Waterhouse 2003; Department of Natural Resources & Mines 2005).

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This database is designed to provide information, including biological and ecological, on invasive plant species that are on a national weed list, or are legislated against in a state or territory. While reasonable efforts have been made to ensure the accuracy of the information, no guarantee is given, nor responsibility taken, by the Commonwealth for its accuracy, currency or completeness. The Commonwealth does not accept any responsibility for any loss or damage that may be occasioned directly or indirectly through the use of, or reliance on, the information contained in this database. The information contained in this database does not necessarily represent the views of the Commonwealth. This database is not intended to be a complete source of information on the matters it deals with. For further information on the images contained in the database please contact the copyright owner. All images in the weed identification tool are managed by the Australian Plant Image Index (APII). Various copyright conditions apply for these images. For further information on the copyright conditions of images contained in the database please contact the APII at: photo@anbg.gov.au.