Quick Facts

Quick facts

  • Originally from the Americas, Alkali Sida (Malvella leprosa) is an invasive perennial herb to 35 cm tall, regrowing each year from roots, with rounded to fan or kidney shaped leaves, and white to yellow flowers.
  • Occurs mainly on alkaline soils in arid, semi-arid, and warm temperate regions of Victoria and South Australia and sparingly in New South Wales.
  • Mainly an agricultural weed, growing in annual crops, irrigated pastures and channel banks, where it competes with pastoral species.
  • Propagates by root fragments and seeds.
  • Root fragments are be spread in contaminated produce, machinery, or soil, which are able to resprout, grow, and produce new plants.
  • Seeds spread by water, on livestock or in contaminated produce, machinery, or soil.
  • It may cause injury to livestock if eaten in quantity, but is rarely grazed.
  • Controlled by repeated application of herbicides when actively growing before flowering preventing seed set.

What Does It Look Like?

What is it?

Alkali Sida (Malvella leprosa) is a semi-erect low-growing perennial herb to 35cm high. Stems are light green and slender, up to 50 cm long, prostrate (lying flat on the ground) to erect, and covered with many star-shaped (stellate) hairs. The leaves are densely covered with the same stellate hairs, giving a grayish-green appearance. Leaves are ovate (shaped like a section through the long axis of an egg and attached by the wider end) to reniform (kidney-shaped) or flabellate (fan-shaped), about 1–3.5 cm long, 1.5–4.5 cm across, asymmetrical at the base, bluntly (with few) large and irregularly rounded teeth. Lower leaf-surface paler and more densely hairy with prominent veins. The leaves are alternately arranged along the stem and borne on short leaf-stalks. Stipules (small appendage at the bases of leaves) lanceolate (lance-shaped), 4.5–6 mm long. Roots are perennial, and can be deep and extensive with new plants growing from roots.

The cream to yellow flowers are 2.5–3.5 cm in diameter, 5-petalled, with each petal up to 1.3 cm long, notched, wavy, or rounded at the tip. Flowers form in leaf axils or in small clusters at the end of the branches on short stalk from 0.5–1.9 cm long. the reproductive structure are  hibiscus-like borne on column with stamens (male reproductive structures) inserted at different level and styles (female reproductive structures) 6–10, borne at the tip. Flowers have the usual calyx (the outer whorl of a flower, usually green) each of the 5 lobes are  6–8 mm long. Each flower has an additional whorl of lobes called an epicalyx, comprised of three linear lobes half the length of the calyx 3–4 mm long, occurring at the base of the calyx.

The fruits are cone- or disc-shaped, about 1–6 mm in diameter,  3.5 mm high, 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 with new plants growing from detached roots (Navie 2004; Jessop 1986; Barker 1996; Parsons & Cuthbertson 2001; VicFlora 2016).

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

Flower colour

White, Yellow

Growth form (weed type/habit)


Where it currently grows? Preferred habitat

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). Not normally associated with native vegetation although it does occur in native ecosystems in some areas.

Are there similar species?

Alkali Sida is similar to members of the genus Sida. The introduced weeds Spinyhead Sida (Sida acuta), Flannel Weed (Sida cordifolia) and Paddy's Lucerne (Sida rhombifolia) have similar flowers to Alkali Sida, but this species differs conspicuously in overall growth form and leaf shape, and by the presence of 1 to 3 linear lobes (epicalyx) at the base of the calyx (Parsons & Cuthbertson 2001).

Spinyhead Sida (Sida acuta) occurs in tropical northern areas in Western Australia, Northern Territory and Queensland in coastal and some inland northern regions and the distribution does not normally overlap with Alkali Sida. Spinyhead Sida is a perennial shrub growing to 1.5 m high, much taller than Alkali Sida. The leaves are spear-head shaped rather than fan-shaped and either without hairs or only sparsely hairy (AVH 2021; Parsons & Cuthbertson 2001).

Flannel Weed (Sida cordifolia) occurs in tropical northern Western Australia, Northern Territory and Queensland, and the distribution does not normally overlap with Alkali Sida. Flannel Weed is also much taller than Alkali Sida, being an erect shrub to 2 m high with erect to ascending stems. The leaves are oblong to egg shaped, and larger, up to 7.5 cm long and up to 6 cm wide. Flowers are dark yellow, often with a dark orange centre (AVH 2021; Parsons & Cuthbertson 2001).

Paddy's Lucerne (Sida rhombifolia) occurs widely in Australia, occurring in all states with the exception of Tasmania, but is not commonly recorded where Alkali Sida occurs. However, it is a taller erect, much branched shrub to 1 m high. The leave blades are oblong to spear-head shaped, not fan-shaped as in Alkali Sida (AVH 2021; Parsons & Cuthbertson 2001).

Why Is It A Weed?

What are its impacts?

Agriculture: 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 (Agriculture Victoria 2021; Parsons 1973; Parsons & Cuthbertson 2001). However, overseas experience suggests that it could compete strongly with irrigated pastures if introduced to this system (Government of South Australia 2021). 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).

Native ecosystems: 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 many native areas apart from riparian areas and riverine grassy woodland and grasslands (Agriculture Victoria 2021).

How does it spread?

Alkali Sida can be dispersed when contaminated patches of soil, containing small root fragments or seeds, are cultivated and transported to clean areas. Root fragments are then capable of producing new shoots and abundant seeds, and seed can germinate in spring. 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).

What is its history in Australia?

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).

How To Manage It?

Best practice management

The best and only methods of control are repeated application of herbicides during active growth before flowering to deplete the large underground roots.

Non-chemical control: While the above-ground vegetation of Alkali Sida dies off in autumn, the root system can be extensive in the soil. The removal of above-ground parts by cultivation is not effective, as resprouting occurs from the root system. Furthermore, excessive cultivation may spread the plant. This species is not readily grazed by livestock, and therefore grazing can encourage its spread due to the removal of competitive species (Parsons & Cuthbertson 2001). Alkali Sida is considered to be moderately palatable to goats, which may be useful for the control of this species in pastoral areas (Meat & Livestock Australia 2007).

Chemical control: The only currently effective control is by herbicides, which should be applied before flowering and during active growth (Parsons & Cuthbertson 2001; Agriculture Victoria 2021). It can be controlled by repeated spot spraying with an appropriate herbicide. Costs are minor for the small infestations in the state, but the herbicide used on Alkali Sida cannot be applied close to vines or horticultural crops due to potential for vapour drift (Government of South Australia 2021).

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)

Seeds of Alkali Sida germinate in spring with rapid growth until summer. Flowering mainly occurs from December to February. Above ground growth then dies back in autumn, and new shoots emerge from buds on the root system in spring. Seedlings grow rapidly and flower within the first year (Barker 1996; Parsons & Cuthbertson 2001; Navie 2004).

Where Is It Found?

Which states and territories is it found?


What areas within states and territories is it found?

In New South Wales Alkali Sida occurs in the Murrumbidgee Irrigation Area. In NSW it is only classed as doubtfully naturalised (APC 2021).

In South Australia it is naturalised on the Yorke Peninsula, the upper north, and the Murray River basin 

In Victoria it is naturalised in the north-west around Mildura, Swan Hill and Kerang areas (AVH 2021; Barker 1996, Parsons & Cuthbertson 2001).

Where does it originate?

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).  Outside of the Americas it has only known to have established as a weed in Australia (USDA 2021).

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

Malvella leprosa

Other scientific names (synonyms)?

  • Malva hederacea Douglas
  • Malva leprosa Ortega
  • Malvella leprosa var. hederacea W.T.Parsons & Cuthbertson
  • Sida hederacea (Douglas) Torr. ex A.Gray
  • Sida leprosa (Ortega) K.Schum.
  • Sida leprosa (Ortega) K.Schum. var. leprosa
  • Sida leprosa var. hederacea (Douglas) K.Schum.
  • Malvella leprosa var. hederacea W.T.Parsons & Cuthbertson

Does it have other known common name(s)?

Ivy-leaf Sida, Alkali Mallow

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