Weeds in Australia


Malvella leprosa


Alkali Sida (Malvella leprosa) is a low-growing to semi-erect perennial herb to 30cm high. Stems are light green and slender, up to 50cm long, prostrate to erect, and covered with star-shaped (stellate) hairs. The leaves are densely covered with the same stellate hairs, giving a greyish-green appearance. Leaves are fan-shaped, about 2.5-3.5 cm across, asymmetrical at the base, bluntly toothed, with prominent veins on the underside. The leaves are alternately arranged along the stem and borne on short stalks. The yellow to cream flowers are 2.5-3.5 cm in diameter, 5-petalled, and form in leaf axils or in small clusters at the end of the branches. Three linear lobes, 3-4 mm long, occur at the base of the calyx. The fruits are cone- or disc-shaped, about 1-6 mm in diameter, divided into several segments, and contain 6-10 seeds. Seeds are dark brown, roughly textured, approximately 2 mm in diameter. Roots are perennial, and can be deep and extensive (Navie 2004; Jessop 1986; Barker 1996; Parsons & Cuthbertson 2001).

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


Alkali Sida occurs in the Murrumbidgee Irrigation Area in New South Wales; north-west Victoria (Mildura, Swan Hill and Kerang areas); and in South Australia where it occurs on the Yorke Peninsula, the upper north, and the Murray River basin (Barker 1996, Parsons & Cuthbertson 2001).

Key points:

  • Alkali Sida (Malvella leprosa) is an invasive species which occurs mainly on alkaline soils in arid, semi-arid, and warm temperate regions of New South Wales, Victoria and South Australia.
  • It currently occurs mostly as an agricultural weed, growing on annual crops, irrigated pastures and channel banks, where it competes with pastoral species.
  • It can spread by the movement of root fragments, which are able to resprout and produce numerous seed. It can also be spread by water, on livestock or in contaminated produce.
  • It may cause injury to livestock if eaten in quantity, but is rarely grazed.

How it spreads:

Alkali Sida can be dispersed when contaminated patches of soil, containing small root fragments, are cultivated and transported to clean areas. These root fragments are then capable of producing new shoots and abundant seeds. Also, capsules (containing seeds) can be transported on the coats of livestock or in clothing. Seed has also been found in contaminated agricultural produce. Capsules and seeds are also effectively dispersed by water (Lamp & Collet 1976; Navie 2004; Parsons & Cuthbertson 2001), and this species establishes well in irrigation channels and can encroach into adjoining pastures (Parsons 1973).

Where it grows:

Alkali Sida occurs in semi-arid, arid, and warm temperate regions of New South Wales, Victoria and South Australia. It is found chiefly in annual crops, irrigated pastures and channel banks, principally on alkaline soils (Parsons 1973; Parsons & Cuthbertson 2001).

Flower colour:Yellow
Distribution map:

AVH 2007 Victoria only: Victorian Resources Online 2007


Alkali Sida is a deep-rooted perennial that competes strongly with pastoral species, especially on alkaline soils. It is thought to impact especially on irrigated annual pastures, and restricts growth and replaces biomass in these areas, as it can form large, dense colonies (California Department of Food and Agriculture 2007). However the current area of infestation in Australia is small, probably has only a minor impact on crop yield, and is not thought to affect land value (Parsons 1973; Parsons & Cuthbertson 2001; Victorian Resources Online 2007).

Although usually avoided by grazing livestock, Alkali Sida can be toxic in large quantities to sheep due to formation of hairball blockages in the intestines (Hill 1993; California Department of Food and Agriculture 2007: Lamp & Collet 1976).

This species may have a minor impact on the flora strata in grassland communities, and potentially reduce the food source of some native fauna. However, it is not currently known to invade native areas (Victorian Resources Online 2007).


Alkali Sida is native to western and southern North America. It has some importance as an agricultural weed in California, Utah and Texas (Parsons & Cuthbertson 2001), and is a declared weed in California and Arizona (as Sida hederacea) (GRIN 2007). It is widely distributed in California, and can be problematic in grain and cotton crops and orchards, and often occurs on disturbed sites (Robbins et al. 1970; Parsons 1973).


The time of introduction of Alkali Sida into Australia is unknown; however, two large patches were reported near Kerang, Victoria, in 1938, leading to its proclamation as a noxious weed in this area (Parsons 1973).


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