Sida (Sida species)

Assessment ID: 1247
Jurisdiction: North Territory
Methodology: Northern Territory Weed Risk Management System - terrestrial
Management area: Tennant Creek and Alice Springs Regions

Notes: Draft technical report available on request from weedinfo@nt.gov.au

Status: PUBLISHED
Last updated: 20/3/2025 2:55:58 pm AEST

Questions answered: 39 / 47

Weed Risk: 147.50 (High)
   Invasiveness (raw/adjusted): 10.00 / 8.330
   Impacts (raw/adjusted): 4.00 / 2.104
   Potential distribution (raw/adjusted): 16.00 / 8.416

Feasibility of Control: 122.33 (High)
   Control costs (raw/adjusted): 7.00 / 6.363
   Current distribution (raw/adjusted): 5.00 / 5.000
   Persistence (raw/adjusted): 5.00 / 3.845

Result: Protect priority sites

Invasiveness

A1. What is the ability of the plant to establish amongst intact native environments?
Answer: High

Comments: (Sida acuta) is a common weed of the Kimberley, occurring in wasteland, creeks and riverine vine thickets (Hussey et al. 1997). Habitat: Disturbed areas. Often found on overgrazed pastures or overused areas, around camp grounds and human settlements. Also weeds of gardens (Smith 2002). Spinyhead sida has become a common weed of degraded land, improved pasture and cultivated areas (Wheaton 1994). (Sida rhombifolia) A pantropical weed, widespread throughout Hawai’i in disturbed areas (Motooka et al. 2003). (Sida rhombifolia) Could be an environmental weed of remnant grassy native vegetation in farming areas (Eurbodalla Shire Council 2007). (Sida rhombifolia)…grows only in disturbed areas and in situations where overhead competition is controlled or naturally light…It does not survive in tall grass swards, tall brush lands and closed forests (Francis n.d.). (Sida acuta) Commonly found in disturbed areas such as over-grazed pastures and over-used areas (Smith 2001). (Sida rhombifolia) principally occurring as a weed in moist disturbed areas on roadsides, in cultivation paddocks, degraded pastures and waste places (Parsons and Cuthbertson 1992). (Sida cordifolia) principally on disturbed lighter soils, occurring as a weed of roadsides, cultivated fields, degraded pastures and waste places (Parsons and Cuthbertson 1992). (Sida acuta) It is also a prominent in the pastures of the disturbed areas of the Top End of the Northern Territory (Parsons and Cuthbertson 1992). (Sida acuta) It occurs as a weed in disturbed areas on a wide range of soil types in cultivated fields, degraded pastures, tree plantations, roadsides and waste places (Parsons and Cuthbertson 1992). (Sida cordifolia) In New Guinea, a weed of abandoned cultivation and pastures, also occurring naturally in savannah (Henty and Pritchard 1975) cited in (Pacific Island Ecosystems at Risk 2006). Additional references available on request from weedinfo@nt.gov.au.

A2. What is the reproductive ability of the plant?

(a) Time to seeding
Answer: 1 year or less

Comments: (Sida rhombifolia) Seeds begin germinating after the opening spring rains in late September or October and, under favourable conditions, seedlings continue to emerge throughout the summer. Young plant establish quickly, flowering and setting seed between December and April (Parsons and Cuthbertson 1992). (Sida acuta) Flowers and fruits April to September (Smith 2001). Arrowleaf sida (Sida rhombifolia) flowers and fruits continuously starting at 3 or 4 months of age in Puerto Rico. In Central India, plants flower from September to December and fruit from October to January Parrotta 2001) cited in (Francis date unknown).

(b) Annual production of viable seed /m2 or /plant
Answer: High

Comments: (Sida rhombifolia)A single plant can produce as many as 11,600 seeds (Francis (date unknown)). All species are prolific seeders (Smith 2002). Spinyhead sida seeds prolifically (Parsons and Cuthbertson 1992). Flannel weed seeds prolifically (Parsons and Cuthbertson 1992). Known to be a prolific seeder (Smith 2001).

(c) Vegetative reproduction
Answer: None

Comments: (Sida acuta) New growth develops from the rootstock at the beginning of the following wet season (Parsons and Cuthbertson 1992). (Sida cordifolia) New shoots form on the perennial rootstock with the return of suitable growing conditions the following spring (Parsons and Cuthbertson 1992). (Sida rhombifolia) New growth appears on the rootstock the following spring and flowering commences almost immediately (Parsons and Cuthbertson 1992).

A3. Do propagules of the plant have properties that allow them to be dispersed long-distance by natural means?

(a) Flying animals (birds, bats)
Answer: Yes

Comments:

(b) Other wild animals
Answer: Yes

Comments: Spread in mud sticking in hooves (Parsons and Cuthbertson 1992). Spinyhead sida is disseminated only by seed which, aided by the two awns at the apex, adhere to wool, fur (Parsons and Cuthbertson 1992). (Sida cordifolia) A few (seeds), eaten by animals, are excreted relatively unharmed often considerable distances from the sources, while others are spread in mud sticking to hooves (Parsons and Cuthbertson 1992). (Sida rhombifolia) the seeds are dispersed by ruminant animals (Francis (date unknown)).

(c) Water
Answer: Yes

Comments: (Sida cordifolia) They (seeds) are also spread by irrigation waters (Parsons and Cuthbertson 1992). (Sida rhombifolia) Seed may be dispersed in irrigation waters and streams (Parsons and Cuthbertson 1992). (Sida rhombifolia) Has been found in the irrigated area at Harvey (Hussey et al. 1997). (Sida rhombifolia) the seeds are dispersed by water (Francis (date unknown)).

(d) Wind
Answer: No

Comments:

A4. How likely is long-distance dispersal by human-assisted means?

(a) Deliberate spread by people
Answer: Unlikely

Comments: Probably introduced late last century by the Chinese who made brooms from its fibrous stems (spinyhead sida) (Pitt 2002). (Sida acuta) May have been introduced by the Chinese miners for use in making brooms (Smith 2001). (Sida acuta) Used by some Aboriginal groups in the Top End in the manufacture of brooms, hence in some areas is not considered an undesirable plant (Smith 2001). Arrowleaf sida (Sida rhombifolia) stems as used as rough cordage, sacking, and for making brooms (Francis (date unknown)). (Sida rhombifolia) the species was introduced into the United States in the last 1800’s as a promising fiber crop (Francis (date unknown)).

(b) Accidentally by people and vehicles
Answer: Common

Comments: The awned mericarps are spread by adhering to clothing in mud on vehicles (Smith 2002). Spinyhead sida is disseminated only by seed which, aided by the two awns at the apex, adhere to clothing and other fibrous materials (Parsons and Cuthbertson 1992). The seed are also spread in…footwear, farm machinery and other vehicles (Parsons and Cuthbertson 1992). (Sida cordifolia) Spread in mud sticking to …footwear, farm machinery and other vehicles (Parsons and Cuthbertson 1992). (Sida rhombifolia) Its finely barbed awns are ideally suited to catch in clothes and other fibrous material (Parsons and Cuthbertson 1992). (Sida rhombifolia) the seeds are dispersed by farm machinery (Francis (date unknown)).

(c) Contaminated produce
Answer: Common

Comments: The awned mericarps are spread as contaminants in hay and seed crops (Smith 2002). Seed may contaminate harvested material (Pitt 2002a, 1998, 2002b). The seeds are also spread as impurities in agricultural produce such as hay and pasture seed (Parsons and Cuthbertson 1992). (Sida rhombifolia) the seeds are dispersed in impure agricultural seed (Francis (date unknown)).

(d) Domestic/farm animals
Answer: Common

Comments: The awned mericarps are spread by adhering to livestock (Smith 2002). Spinyhead sida is disseminated only by seed which, aided by the two awns at the apex, adhere to wool, fur (Parsons and Cuthbertson 1992). It is also spread when seed ingested by stock is excreted in a viable condition (Parsons and Cuthbertson 1992). (Sida rhombifolia) Its finely barbed awns are ideally suited to catch in wool, fur… (Parsons and Cuthbertson 1992).

Impacts

B1. What is the plant's competitive potential?
Answer: Low

Comments: (Sida rhombifolia) Can be competitive in pasture, due to its unpalatability to livestock (Eurbodalla Shire Council NSW 2007). (Sida rhombifolia) Infests mesic to wet pastures and many crops worldwide in temperate and tropical zones (Motooka et al. 2003). Invasive unpalatable shrubs that compete with and exclude more desirable native species on degraded or overused land (Smith 2002). (Sida acuta) Invasive unpalatable shrubs that compete with an exclude more desirable native species on degraded or over utilised land (Smith 2001). (Sida acuta and Sida rhombifolia) It competes with desirable species (Wheaton 1994). (Sida acuta and Sida cordifolia) Sida rapidly infests overgrazed areas near troughs and underneath shade trees. As soil nitrogen builds up under legume pasture sida spreads over the paddock, competing with more palatable pasture species (Department of Agriculture and Food WA 2007). Where there is a pronounced wet and dry season, paddy’s lucerne, because of its deep root system, tends to continue active growth longer than other species, giving it a competitive advantage because of the longer time during which it can ripen seeds (Parsons and Cuthbertson 1992). (Sida rhombifolia) It is a common component of pastures on the east coast of Australia, smothering all grasses in some cases (Parsons and Cuthbertson 1992). Additional references available on request from weedinfo@nt.gov.au.

B2. What is the plant’s potential to modify the existing fire behaviour and alter the fire regime?
Answer: No potential

Comments:

B3. What is the plant’s potential to restrict the physical movement of people, animals, vehicles, machinery and/or water?
Answer: Low

Comments:

B4. What is the plant’s potential to negatively affect the health of animals and/or people?
Answer: Low

Comments: (Sida rhombifolia) It is not poisonous, but when animals eat it, there is always a danger of ‘hair-balls’ forming from the stringy bark. At the same time it is known to have caused the death of humans and poultry, because of the internal irritation set up by the barbed awns on ingested seed (Parsons and Cuthbertson 1992). (Sida rhombifolia) Dangerous for cattle because its fine fibres form hair-balls in the intestine; nutlets also harmful (mechanically) to poultry (Soerjaniet al. n.d.). Paddy’s lucerne has, occasionally, been used medicinally in parts of Asia and is sometimes grown in India as a substitute to jute (Parsons and Cuthbertson 1992). Paddy’s lucerne is used in Indonesia for various medical complaints such as toothache, ulcers and as an abortifacient. Cultivated in India for its fibre (Smith 2002). (Sida rhombifolia) Used as a fibre source and as a medicinal in some parts of the world (Motooka et al. 2003).

B5. Does the plant potentially have negative effects on natural and cultural values?

(a) Reducing habitat quality for native animals?
Answer: Medium

Comments:

(b) Threatened species or communities
Answer: None identified

Comments:

(c) Sites of natural or cultural significance
Answer: None identified

Comments:

B6. Is the plant presumed to have negative effects on environmental health?

(a) Soil chemistry/stability
Answer: No

Comments:

(b) Water quality
Answer: No

Comments:

(c) Hydrology
Answer: No

Comments:

Potential distribution

C1b. What is the Climatch suitability score (which indicates the proportion of the NT environment that is suitable for the plant)?
Answer: 10

Comments: Although it grows widely throughout the tropics, it can be found at higher elevations. It has been reported up to 1,500 m in Indonesia. The plant grows well in many soils, including some heavy clays, and can tolerate dry as well as high rainfall conditions. In Fiji it is most aggressive in the dry zones (Sida acuta) (Pacific Island Ecosystems at Risk 2007). The Sidas have spread throughout the tropics and sub-tropics in Australia. It is widespread in the higher rainfall areas from Brisbane in Queensland through the Northern Territory to the Ord River region of Western Australia (Wheaton 1994). Today it is widespread in higher rainfall areas from Brisbane in Queensland to the Ord River region of Western Australia (Flanagan et al. 2000). Sida is found on most soil types except some of those derived from limestone and seasonally flooded clays. It can be found throughout the warm regions of the world. Sida is a weed of tropical pasture, when native pastures are fertilised with superphosphate and seeded with pasture legumes such as Townsville Stylo….in WA, Sida has been found in rangelands in the East and West Kimberley (Department of Agriculture and Food WA 2007). Arrowleaf sida (Sida rhombifolia) grows on both fertile and degraded soils of all textures and derived from most parent materials. It may be found growing from near sea level to 2000 m in elevation. In Puerto Rico, the species grows in areas receiving from 900 to 3000 mm of precipitation (Francis n.d.). Additional references available on request from weedinfo@nt.gov.au.

C2. How many broad habitat types in the NT will the plant potentially naturalise in (up to 5)?
Answer: Four

Comments:

C3. What is the potential of the plant to occur throughout its favoured habitat in the NT (as identified in question 2)?
Answer: Some

Comments:

Control costs

A1. How detectable is the weed?

(a) Distinguishing features
Answer: Sometimes distinct

Comments: Spinyhead sida (Sida acuta): Stems to c.1.5m high. Leaves bright green. Flowers pale yellow. Fruit domed in centre, mericarps 5-7, each with 2 sharp awns c.1/5 mm long. Flowers/fruits April – September. Flannel weed (Sida cordifolia): Stems to 1 m high, covered with dense soft hairs. Leaves softly hairy, prominent veins impressed on upper surface. Flower yellow-reddish at base. Fruit ovid, 6-8 mm in diameter, 10 mericarps, each with 2 conspicuous bristles about 3 mm long. Flowers/fruits mainly December- May. Paddy’s lucerne (Sida rhombifolia): Stems to 1 m high and a deep taproot. Leaves dull green. Flowers yellow to pale orange on thin stalks to 4 cm long. Fruit ovoid, 5-6 mm in diameter, mericarps 9-12, each with 2 ribs on back and 2-awned (Smith 2002).

(b) Active growth period
Answer: <4 months

Comments:

(c) Height at maturity
Answer: 0.5 - 2 m

Comments: (Sida acuta) A perennial herb, or small shrub to 60 cm (Hussey et al. 1997). (Sida rhombifolia) commonly growing to 60cm but sometimes reaching 1.5m in height (Francis (date unknown)). (Sida rhombifolia) … erect shrub, to 5 ft (Motookaet al. 2003). (Sida acuta and cordifolia)…small shrub up to 1.5 metres tall (Department of Agriculture and Food WA 2007).

A2. What is the general accessibility of infestations at the optimum treatment time?
Answer: High

Comments:

A3. How expensive is control of the weed in the first year of targeted control, for an infestation that has reached maximum weed density?

(a) Chemical costs
Answer: Low

Comments:

(b) Labour cost
Answer: Low

Comments:

(c) Equipment cost
Answer: Medium

Comments:

A4. What is the general community perception of this weed within the region?
Answer: Medium

Comments: (Sida acuta) Used by some Aboriginal groups in the Top End in the manufacture of brooms, hence in some areas is not considered an undesirable plant (Smith 2001).

Current distribution

B1. What is the current pattern of the species’ distribution across the weed management region?
Answer: Scattered

Comments:

Persistence

C1. How long will it take to reach the maintenance period?
Answer: Medium

Comments:

C2. What is the minimum time period for reproduction of sexual or vegetative propagules?
Answer: <1 growing season

Comments: (Sida acuta) (Sida cordifolia) Plants establish rapidly in the absence of competition, flower in mid-to late Summer and mature seed in autumn (Parsons and Cuthbertson 1992). (Sida rhombifolia) Seeds begin germinating after the opening spring rains in late September or October and, under favourable conditions, seedlings continue to emerge throughout the summer. Young plant establish quickly, flowering and setting seed between December and April (Parsons and Cuthbertson 1992). (Sida acuta) Flowers and fruits April to September (Smith 2001). Arrowleaf sida (Sida rhombifolia) flowers and fruits continuously starting at 3 or 4 months of age in Puerto Rico. In Central India, plants flower from September to December and fruit from October to January (Parrotta 2001) cited in (Francis (date unknown)).

C3. What is the maximum longevity of sexual or vegetative propagules?
Answer: 2-5 years

Comments: (Sida acuta)…Most (seeds) are dormant when shed, providing a long-term seed pool which gives rise to seedlings over many years (Parsons and Cuthbertson 1992). (Sida acuta) there appears to be a long-term dormant seed pool which can give rise to new generations of seedlings (Mott 1980).

C4. What is the threat of reinfestation from outside the management region?

(a) Long-distance (>100m) dispersal by natural means
Answer: Frequent

Comments: Spread in mud sticking in hooves (Parsons and Cuthbertson 1992). Spinyhead sida is disseminated only by seed which, aided by the two awns at the apex, adhere to wool, fur (Parsons and Cuthbertson 1992). (Sida cordifolia) A few (seeds), eaten by animals, are excreted relatively unharmed often considerable distances from the sources, while others are spread in mud sticking to hooves (Parsons and Cuthbertson 1992). (Sida rhombifolia) the seeds are dispersed by ruminant animals (Francis (date unknown)). spread in…mud sticking in hooves (Parsons and Cuthbertson 1992). Spinyhead sida is disseminated only by seed which, aided by the two awns at the apex, adhere to wool, fur (Parsons and Cuthbertson 1992). (Sida cordifolia) A few (seeds), eaten by animals, are excreted relatively unharmed often considerable distances from the sources, while others are spread in mud sticking to hooves (Parsons and Cuthbertson 1992). (Sida rhombifolia) the seeds are dispersed by ruminant animals (Francis (date unknown)). (Sida cordifolia) They (seeds) are also spread by irrigation waters (Parsons and Cuthbertson 1992). (Sida rhombifolia) Seed may be dispersed in irrigation waters and streams (Parsons and Cuthbertson 1992). (Sida rhombifolia) Has been found in the irrigated area at Harvey (Hussey et al. 1997). (Sida rhombifolia) the seeds are dispersed by water (Francis (date unknown)).

(b) Long-distance (>100m) dispersal by human means
Answer: Occasional

Comments: The seed are also spread in…footwear, farm machinery and other vehicles (Parsons and Cuthbertson 1992). It is also spread when seed ingested by stock is excreted in a viable condition (Parsons and Cuthbertson 1992). Spinyhead sida is disseminated only by seed which, aided by the two awns at the apex, adhere to wool, fur (Parsons and Cuthbertson 1992). The awned mericarps are spread by adhering to livestock (Smith 2002). (Sida rhombifolia) the seeds are dispersed in impure agricultural seed (Francis (date unknown)). The seeds are also spread as impurities in agricultural produce such as hay and pasture seed (Parsons and Cuthbertson 1992). Seed may contaminate harvested material (Pitt 2002a, 1998, 2002b). The awned mericarps are spread as contaminants in hay and seed crops (Smith 2002). (Sida rhombifolia) the seeds are dispersed by farm machinery (Francis (date unknown). (Sida cordifolia) Spread in mud sticking to …footwear, farm machinery and other vehicles (Parsons and Cuthbertson 1992). Spinyhead sida is disseminated only by seed which, aided by the two awns at the apex, adhere to clothing and other fibrous materials (Parsons and Cuthbertson 1992). The awned mericarps are spread by adhering to clothing…in mud on vehicles (Smith 2002). (Sida rhombifolia) the species was introduced into the United States in the last 1800’s as a promising fiber crop (Francis (date unknown)). Arrowleaf sida (Sida rhombifolia) stems as used as rough cordage, sacking, and for making brooms (Francis (date unknown)). (Sida acuta) Used by some Aboriginal groups in the Top End in the manufacture of brooms, hence in some areas is not considered an undesirable plant (Smith 2001). (Sida acuta) May have been introduced by the Chinese miners for use in making brooms (Smith 2001). Additional references available on request from weedinfo@nt.gov.au.

References

Eurbodalla Shire Council New South Wales. (2007). Paddy's Lucerne (Sida rhombifolia) http://www.esc.nsw.gov.au/Weeds/Sheets/herbs/H%20Paddy's%20lucerne.htm. Accessed 18/09/07. Pacific Island Ecosystems at Risk. (2007). Sida acuta. http://www.hear.org/Pier/species/sida_acuta.htm Accessed 17/09/07. Soerjani, M., Kostermans, A. J. H. G. and Tjitrosoepomo, G. (date unknown) Weeds of Rice in Indonesia. Balai Pustaka Indonesia Department of Agriculture and Food WA. (2007). Declared plants - Sida (Sida acuta and Sida cordifolia). http://agspsrv34.agric.wa.gov.au/dps/version02/01_plantview.asp?page=8&contentID=65& Accessed 18/09/07. Flanagan, G. J., Hills, L. A. and Wilson, C. G. (2000). The successful biological control of spinyhead sida, Sida acuta [Malvaceae], by Calligrapha pantherina (Col: Chrysomelidae) in Australia's Northern Territory. Montana State University, Bozeman, Montana, USA. Francis, J. K. (date unknown). Sida rhombifola US Department of Agriculture, Forest Service, Rio Piedras. Motooka, P., Castro, L., Nelson, D., Nagai, G. and Ching, L. (2003). Weeds of Hawaii’s Pastures and Natural Areas: An Identification and Management Guide. College of Tropical Agriculture and Human Honolulu, Hawai'i Mott, J. J. (1980). Germination and establishment of the weeds Sida acuta and the Pennisetum pedicellatum in the Northern Territory. Australian Journal of Experimental Agriculture and Animal Husbandry 20: 463-469. Pacific Island Ecosystems at Risk. (2006). Sida cordifolia. http://www.hear.org/Pier/species/sida_cordifolia.htm Accessed 17/09/07. Pacific Island Ecosystems at Risk. (2007). Sida rhombifolia http://www.hear.org/Pier/species/sida_rhombifolia.htm. Accessed 17/09/07. Additional references available on request from weedinfo@nt.gov.au.