Quick Facts

Quick facts

• Originally from western North America, Poverty Weed (Iva axillaris) is a perennial herb, that grows mostly to 20–40 cm high.
• Produces extensive rhizomes, is colony forming, inhibits other species, and is a strong competitor.
• It is known from several relatively localised sites in South Australia (now eradicated) and Victoria.
• Its known impacts in Australia are chiefly agricultural
• Cultivation is not recommended as it spreads root fragments and mechanical control in ineffective.
• The most effective means of control appears to be the use of herbicides.

What Does It Look Like?

What is it?

Poverty Weed (Iva axillaris) is a perennial herb, mostly 20-40 cm high, with extensive horizontal and vertical underground stems (rhizomes), to 2.5 metres deep, which forms colonies. There are multi stems, which are branched near their bases. The stems are often partially trailing near the base, then upright , but stem are sparsely branched. The lower leaves are oppositely arranged and the upper leaves are alternately arranged on the stem. The leaves are stiff, almost stalkless or very shortly stalked, leaves ovate (egg-shaped attached at the wider end) to elliptic to oval, mostly 10-30 mm long and 3-10 mm wide, smooth margins (without teeth or lobes),  leaf-surfaces with appressed pubescent hairs (covered with downy short soft hairs), grey-green above and below, leaf tip sharply to bluntly pointed, leaf base narrowing to the base. The leaves emit a strong unpleasant odour, particularly when crushed.

The inconspicuous flower-heads are in leafy spikes or racemes ( an indeterminate inflorescence in which the main axis produces a series of flowers on lateral stalks, the oldest at the base and the youngest at the top) Flower-heads are borne individually on short drooping stalks 2-15 mm long in the forks of the upper leaves. Flowers (florets) are greenish-yellow tubular florets, 4-6 mm across. The groups of florets (flower-head) are surrounded by leaf-like bracts (involucral bracts) that are ovate (egg-shaped attached at the wider end), about 3 mm long,  fused (joined) to each other for more than half their length, with a blunt tip and are hairy.

The fruits or 'seeds' (cypselas) are ovoid (egg-shaped), but pointed at one end, 1-3 mm long, flattened on the inner face, and brown to dark-grey, without a tuft of hairs at the top (Cooke 1986; Jeanes 1999; Navie 2004). Six or seven seeds are produced by each flower head.

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

Flower colour

Yellow and Green

Growth form (weed type/habit)

Herb

Where it currently grows? Preferred habitat

In its natural habitat in western North America, Poverty Weed prefers soils with poor drainage, seasonally wet areas, alkaline regions, and saline areas such as salt marshes, and an altitude from 10 to 2500 metres above sea level. It is also frequently a weed in cultivated fields. Although it prefers alkaline and saline soils, it is not confined to these soil types. In the United States of America, Poverty Weed is a natural component of many grassland communities that are subject to occasional fires, for which it is adapted (Bassett et al. 1962; Parsons & Cuthbertson 2001; Northern Prairie Wildlife Research Center 2006; Strother 2006; Department of Primary Industries 2007).

In Australia, Poverty Weed has been reported to invade neglected vineyards, orange groves, pasture, cropping land and roadsides, occurring in areas with an annual rainfall between 300 and 600 mm (Parsons & Cuthbertson 2001).

Are there similar species?

Poverty weed may sometimes appear similar to Centipeda cunninghamii and Centipeda minima. However, neither of these native species has drooping flower heads and both have toothed leaf margins. Centipeda minima also has a more creeping habit (Navie 2004).

Why Is It A Weed?

What are its impacts?

Poverty Weed (Iva axillaris) is a highly invasive weed that is mainly a weed of agriculture. It is a strong competitor and reduces crop yields (Richardson et al. 2007) and has also been reported as aggressively competing with native species (Richardson et al. 2007) The roots reach 2.5 metres deep consisting of both vertical and horizontal roots. Poverty Weed colonises cultivated land or overgrazed pastures. Aerial growth dies in autumn leaving the potential for surface soil erosion (Agriculture Victoria 2021).

Agriculture: The extensive rhizome system produced by Poverty Weed allows it to strongly compete with crops, especially cereals, for water and nutrients. Rots extent for Both the above ground parts of the plant and the roots and rhizomes are known to reduce germination of other species, a potential threat to crop and pasture (Parsons & Cuthbertson 2001). The plant is not thought to be toxic but, as it has a strong disagreeable scent, it is rarely grazed (Parsons & Cuthbertson 2001).

Native ecosystems: There is almost no information available about the impacts that the species has or potentially may have on Australian native ecosystems. Because Poverty Weed can form extensive clonal colonies, it has the potential to displace native grasses/forbs in open situations, particularly where there has been some disturbance. It has been assessed as posing a moderately high threat to Plains Grassy Woodland in the Wimmera bioregion. As the species prefers saline areas, it may also pose a threat to saline ecosystems, such as salt marsh communities (Department of Primary Industries 2000; Stajsic 2008 pers. comm.).

Urban areas: In North America, Poverty Weed has been reported to cause contact dermatitis, and its pollen apparently exacerbates hay fever (Parsons & Cuthbertson 2001; Northern Prairie Wildlife Research Center 2006).

How does it spread?

Poverty Weed reproduces mainly by rhizome fragments and rarely by seed. It produces a large quantity of seed, but in North America the seeds are thought to be rarely viable. One of the most likely reasons for this is that plants are not capable of self pollination. Given that many field infestations probably arise from one clone spreading by rhizomes, low seed set is not unexpected. The seeds are not adapted for wind-dispersal (Bassett et al. 1962; Parsons & Cuthbertson 2001). Vegetative spread by root fragments is the chief means of reproduction. Root fragments are commonly spread by machinery dragging rhizome fragments from infested areas to clean areas (Parsons & Cuthbertson 2001).

What is its history in Australia?

The earliest specimens of Poverty Weed held in an Australian herbarium are two 1926 specimens from Newstead in central Victoria (National Herbarium of Victoria 2008). In South Australia, Poverty Weed was first reported in 1933 at Sevenhill, where it was thought to have been present for at least eight years (Parsons & Cuthbertson 2001).

How To Manage It?

Best practice management

The extensive and deep network of rhizomes, as well as the colonising habit of the species make eradication and control difficult. The movement of agricultural seeds, grain, forage, fodder, soil and machinery contaminated with seeds, and particularly rhizome fragments, from infested areas to clean areas needs to be restricted (EPPO 2001). To help prevent weed spread, good farm hygiene practices should be followed, such as cleaning soil and crop debris from machinery, clothes and shoes before moving between fields and farms (Spora & Johnson 2002).

Chemical control: Because mechanical disturbance of infestations will only exacerbate the problem, herbicide application appears to offer the main effective means of control (Bassett et al. 1962; Williamson 1996; Parsons & Cuthbertson 2001). Effective control may be achieved by using a combination of herbicides, sprayed in summer, during the active growth period of the species. Follow up management may need to be continued for several years to treat any resprouting from rhizomes (Parsons & Cuthbertson 2001).

Please see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au 

Non-chemical control: Physical control:  Hand pulling is difficult leaving viable root system with frequent hand-pulling required for regrowth. In addition plants  may cause allergic symptoms in people and gloves should be worn at all times. 

Does it have a biological control agent?

NO

When does it grow? (lifecycle/growth calendar)

Poverty Weed is a perennial species. It reproduces mainly by its spreading rhizomes, and its seeds are rarely viable. In Australia, new shoots are produced from rhizomes each spring. It is quite likely that seeds also germinate during spring (Parsons & Cuthbertson 2001). New plants develop from lateral roots in spring each year. Flowering has been observed during summer, and the above ground part of the plant dies off in autumn (Bassett et al. 1962; Parsons & Cuthbertson 2001).

Where Is It Found?

Which states and territories is it found?

SA, VIC

What areas within states and territories is it found?

Poverty Weed has a very limited distribution in Australia, even though the species has been present at least since 1926.

The species was known to be previously naturalised in South Australia at Riverton and Sevenhill, but was eradicated decades ago and has not reappeared.

Mostly from a few locations northern Victoria (Navie 2004; AVH 2008). In Victoria known only by a few collections from the Kerang, Quambatook and Swan Hill areas and an old specimen from Newstead. Collected from pasture and fallow land (VicFlora 2016).

Where does it originate?

Poverty Weed is native to western North America, mainly west of the Continental Divide. It occurs from southern British Columbia to California and New Mexico, and eastward to South Dakota (Bassett et al. 1962; GRIN 2008). Outside North America, Poverty Weed has not naturalised on any other continent except Australia (Parsons & Cuthbertson 2001; GRIN 2008).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

NO

Where is it a declared weed?

VIC

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

Iva axillaris

Other scientific names (synonyms)?

• Iva axillaris subsp. robustior (Hook.) Bassett
• Iva axillaris var. robustior Hook.

Does it have other known common name(s)?

Death Weed, Devil's Weed, Mouse-ear Poverty Weed, Poverty Sumpweed.