Quick Facts

Quick facts

  • Flannel Weed (Sida cordifolia) is one of the most serious weeds of crops and pastures in the Top End of the Northern Territory.
  • Flannel Weed is common in disturbed sites such as roadside verges (not just in overgrazed and cultivated country.
  • Plants are rarely eaten by stock.
  • Flannel Weed is a prolific seeder and seed are readily dispersed.

What Does It Look Like?

What is it?

Flannel Weed (Sida cordifolia) is an upright herb or subshrub about 0.3–3 m tall, and is as wide as tall when a shrub. The stem is woody, branching several times and with a well developed tap root. The leaves of Flannel Weed are heart shaped with serrated margins and have a dense covering of hairs which give a light green, felt-like appearance, and are up to 65 mm long.

Flowers are about 15–18 mm across, yellow or orange, and are borne in dense clusters at the end of branches. The outer whorl of the flowers (the calyx) enlarges and encloses the mature fruit, leaving only the awns on the mericarps showing. Petals are yellow or orange throughout or sometimes have a deeper orange or reddish centre and are longer than the calyx, being 7–8 mm long. The fruit, or seed capsule, divides into 10 portions (the mericarps). Each mericarp has two fine bristles at one end (Barker, unpublished manuscript; Pitt 2002). These bristles have a number of stiff downward-pointing hairs along their length, which allow the mericarps to become attached to objects and to thus act as a seed dispersal unit.

Also see Wilson et al. (1995), Smith (2002) and Navie (2004).

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

Flower colour

Yellow, Orange

Growth form (weed type/habit)

Herb, Shrub

Where it currently grows? Preferred habitat

Flannel Weed is common in disturbed tropical and subtropical open forest (savanna), particularly on disturbed lighter soils. It is common along roadside verges, over-used campsites, around watering holes and in overgrazed pastures (Navie 2004).

Are there similar species?

Flannel Weed is most likely to be confused with other species of Sida, especially Spinyhead Sida (S. acuta) and Paddy's Lucerne (S. rhombifolia). Smith (2002) provided illustrations comparing leaves and mericarps of each of these species. Of those Sida that have awns, Flannel Weed is readily distinguished from the rest as its awns have retrorsely (bent and pointing downwards) barbed spines, while Spinyhead Sida, Paddy's Lucerne and S. spinosa awns lack spines (but may be hairy). Furthermore, the leaves of Flannel Weed are densely hairy on both surfaces, while in Spinyhead Sida and Paddy's Lucerne mature leaves are glabrous or sparsely hairy on both surfaces, or sparsely hairy on the upper surface and densely hairy on the lower surface (Barker, unpublished manuscript).

Species of Malvastrum, which may also be confused with Flannel Weed, can be distinguished from Sida because flowers have what is known as an epicalyx, in this case three, free segments situated immediately below the calyx. Species of Sida lack an epicalyx (Barker, unpublished manuscript.).

Why Is It A Weed?

What are its impacts?

Flannel Weed was included in the list of 71 species that were nominated by state and territory governments for assessment as Weeds of National Significance (WONS). Following an assessment process, Flannel Weed was not included as one of the 20 WONS. However, it remains a weed of potential national signficance.

Flannel Weed is a serious weed in a wide range of tropical and subtropical crops; ranging from rice in Brazil to pineapple in South Africa, pastures in Papua New Guinea and cotton, pastures, sugarcane and tobacco in Australia. In the Northern Territory, together with Spinyhead Sida (Sida acuta), Flannel Weed occasionally dominates over-grazed pastures, especially around water troughs and stockyards. These weeds are probably the most serious competitors of sown pasture in the moister northern parts of Australia. They are rarely eaten by stock which, grazing the more palatable species to a greater extent, give these weeds a competitive advantage that is increased by their deep root systems which extend their growing season beyond that of their shallower rooted competitors (Parsons & Cuthbertson 2001).

Flannel Weed invades grasslands and open woodlands (Navie 2004). Like Spinyhead Sida (Sida acuta) and Paddy's Lucerne (Sida rhombifolia) it can compete with and exclude native species on degraded or overused land (Smith 2002).

How does it spread?

Flannel Weed is spread by seed which is contained within awned mericarps. The barbed awns readily adhere to clothing and animal hair. They are also spread by water and as impurities in agricultural produce such as hay and seed, and in mud attached to farm machinery and vehicles. Seed consumed by animals are excreted relatively undigested, thus allowing them to be dispersed as viable seed well away from their source (Parsons & Cuthbertson 2001).

What is its history in Australia?

It is not known when, why or how Flannel Weed was introduced into Australia. It may have been introduced accidentally (Smith 2002), or is possibly native to the tropical regions of Australia (Parsons & Cuthbertson 2001).

How To Manage It?

Best practice management

Small outbreaks of Flannel Weed can be grubbed out before flowering, with care being taken to cut the root well below the surface to prevent or minimise regrowth. Larger areas can be controlled through repeated cultivation but this may not be practical. General slashing of plants before flowering helps reduce seed production in infected areas. The spread of seed from infected paddocks to uninfected paddocks can be reduced if stock are yarded for four to five days beforehand, this allowing time for digested seed to have been excreted and seed attached to their hides to have been brushed off. The sowing of well-fertilised "improved" pastures results in a more dense pasture which inhibits the growth of Flannel Weed. However, care should be taken when deciding what to plant as some other pasture species, such as Buffel Grass, are also serious environmental weeds.

Flannel Weed has 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. Biocontrol agents for Flannel Weed are being investigated (Parsons & Cuthbertson 2001).

Flannel Weed seedlings are susceptible to several herbicides but plants become resistant as they mature (Parsons & Cuthbertson 2001). Please see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au .

Does it have a biological control agent?


When does it grow? (lifecycle/growth calendar)

In northern Australia seeds of Flannel Weed germinate at the onset of the wet season or following good rains during the build-up, from about October to December. Flowering mostly occurs in the late summer although from specimens at the Northern Territory Herbarium it is evident that flowering may occur from March to November (Short 2007, pers. comm.). Plants usually die back at the onset of the dry season; and only plants in favourable conditions will flower during this time of the year. Seed remains dormant for long periods (Parsons & Cuthbertson 2001).

Where Is It Found?

Which states and territories is it found?


What areas within states and territories is it found?

Flannel Weed is predominantly found in northern Australia, in a broad band from the Kimberley region of Western Australia, through the top end of the Northern Territory and northern Queensland, but also extending along the east coast to northern New South Wales. Isolated occurrences are also recorded in the southern Northern Territory and northern South Australia (Navie 2004).

Where does it originate?

Flannel Weed is originally from tropical regions in Central and South America (Pitt 2002).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?


Where is it a declared weed?


Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?


Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?


Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Sida cordifolia

Other scientific names (synonyms)?

Sida densiflora Domin

Does it have other known common name(s)?

Sida, Flannel Sida, Heartleaf Sida

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