Quick Facts

Quick facts

• 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.

What Does It Look Like?

What is it?

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; NSW DPI 2020).

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 vegetatively from the flower head (van Steenis 1954; Haynes & Holm-Nielsen 1986; Sainty & Associates 2002; CRC 2003; GISD 2005; NSW DPI 2020; Weeds Australia undated).

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

Flower colour

Yellow

Growth form (weed type/habit)

Herb, Aquatic

Where it currently grows? Preferred habitat

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 (NSW DPI 2020).

Are there similar species?

There are several native and introduced species that are large, emergent, broad-leafed plants (usually perennials) with large, longitudinally veined leaf blades on bare stalks like Yellow Burrhead. Most of these can be distinguished from Yellow Burrhead when in flower by their bigger flower heads with numerous smallish white or pale pink flowers – this includes species of Alisma, Damasonium minus, species of Caldesia, and Sagittaria platyphylla (all in family Alismataceae).

Butomopsis latifolia, a Northern Territory native in family Limnocharitaceae (possibly also occurring in Queensland, and widespread in the tropics from South-east Asia to Africa), has more slender leaf and flower stalks, generally narrower leaf blades (1–7 cm wide) with up to 7 main longitudinal veins, and clusters of 7-25 or more white flowers (Cowie et al. 2000; Holmes et al. 2005).

Water Poppy (Hydrocleys nymphoides), naturalised in Queensland and Victoria, is in the same family as Yellow Burrhead but its leaves are floating to emergent and smaller (up to 12 cm across) while its 3-petalled yellow flowers are single (not in clusters) and bigger (up to 8 cm across) (Stephens & Dowling 2002; Sainty & Jacobs 2003).

Vegetatively, Yellow Burrhead can look rather like a Giant Water Hyacinth (Eichhornia crassipes), but that is usually a free-floating plant and has striking blue-violet flowers in a spike-like flower head (Sainty & Jacobs 2003; Wilson & Kodela 2007, pers. comm.).

Why Is It A Weed?

What are its 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; NSW DPI 2020). 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 (The State of Queensland 2021). Clumps of the weed provide suitable breeding sites for disease-carrying mosquitoes (GISD 2005).

Agriculture: 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; The State of Queensland 2021).

Native ecosystems: 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; The State of Queensland 2021; NSW DPI 2020).

How does it spread?

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; NSW DPI 2020).

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).

What is its history in Australia?

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; The State of Queensland 2021).

How To Manage It?

Best practice management

Yellow Burrhead is one of the species targeted for national eradication under the National Resource Management Ministerial Council's National Cost-Sharing Eradication Programmes. These programmes map and monitor the full distribution of the species, and coordinate or undertake activities to eradicate that species from Australia. Eradication programs for Yellow Burrhead have been undertaken in Centenary Lakes, Cairns, and the Townsville district (Sainty & Associates 2002).

Chemical control: Varieties of Yellow Burrhead have demonstrated herbicide resistance in Malaysia and Indonesia (Heap 2005). See the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au.

Non-chemical control: Physical control: With unusual foliage and attractive flowers, Yellow Burrhead is likely to be lurking unrecognised in suburban backyards, especially those featuring 'Asian water gardens'. Early detection and measures to prevent the spread of this weed are the best ways to control it. Report any findings to your local authority or weed management agency. Specimens will need to be positively identified at your state or territory herbarium, and specialist assistance should be sought to minimise the risk of accidental dispersal of the tiny seeds. All occurrences must be reported and fully documented before removal, to facilitate follow-up as part of the national eradication campaign. Infested sites need ongoing inspection to prevent re-infestation from the seed bank (CRC 2003).

Prevention: Yellow Burrhead is banned from being imported into Australia, and should not be sold by plant nurseries or cultivated in ponds and water gardens (The State of Queensland 2021; NSW DPI 2020).

For further management and control information see CRC (2003), Waterhouse (2003), GISD (2005), The State of Queensland (2021) and NSW DPI (2020).

Does it have a biological control agent?

NO

When does it grow? (lifecycle/growth calendar)

Yellow Burrhead flowers and fruits all year round. The flowers open in the morning and close after a few hours. Yellow Burrhead is an annual in ephemeral waterbodies and sites with pronounced dry seasons (van Steenis 1954).

Where Is It Found?

Which states and territories is it found?

QLD

What areas within states and territories is it found?

Yellow Burrhead is naturalised in north-eastern Queensland: in the Cairns area, and near Feluga, Mossman and Townsville (The State of Queensland 2021). 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).

Where does it originate?

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).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

NO

Where is it a declared weed?

NSW, NT, QLD, WA

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

Limnocharis flava

Other scientific names (synonyms)?

Alisma flavum L.

Limnocharis emarginata Humb. & Bonpl.

Does it have other known common name(s)?

Yellow Bur-head, Limnocharis, Yellow Sawah Lettuce, Sawah-flower Rush, Sawah Flowering Rush, Water Cabbage, Yellow Velvetleaf, Velvetleaf