Quick Facts

Quick facts

• Originally from Mexico, Crofton Weed (Ageratina adenophora) is an aggressive weed of pastures and of cleared areas, and open and riparian areas.
• Crofton Weed also affects crop yield and reduces the ecological value of bush land.
• It sets a prolific number of readily dispersed seeds.
• Crofton Weed is poisonous to horses causing death.
• Controlled by slashing and mowing normally followed by herbicide treatments.
• Can be removed manually, but the underground crown (growing point) must be dug-up and removed.
• Lack of accessibility for mechanical and chemical control of plants growing on steep land, plus the susceptibility of biological control agents to native parasitic insects, means that Crofton Weed still persists in significant amounts.

What Does It Look Like?

What is it?

Crofton Weed (Ageratina adenophora) is a many-stemmed, perennial herb to sub-shrub, often 1 to 2.5 m tall and with purplish, erect, smooth stems which are shortly branched towards the apex. Its roots are pale yellow and have a carrot-like smell when broken. The stems are glandular hairy when young. Leaves are opposite, dark green, rhombic (somewhat diamond-shaped or trowel-shaped), 30 to 120 mm long and 30 to 70 mm wide, a little rough with small stiff hairs, with roughly toothed margins (serrate).

Flowers are in cluster of 40-50 (as like other daisy plants), flowers about 3.5–4 mm long, white, and are grouped together in heads, heads about 5 to 6 mm in diameter and these are in turn grouped together in clusters at the end of the branches. Each flower produces a seed with many seeds produced on a flower-head.

The fruits or 'seeds' (cypselas) are dark brown to black, angular, and about 1.5 to 2 mm long and at their apex have about 5 to 10 white hairs about 4 mm long (Parsons & Cuthbertson 2001; Navie 2004).

Also see Parsons & Cuthbertson (2001), Trounce & Dyason (2003), Navie (2004), Land Protection (2006), PIER (2007) for illustrations or photographs. For further information and assistance with identification of Crofton Weed contact the herbarium in your state or territory.

Flower colour

White

Growth form (weed type/habit)

Shrub, Herb

Where it currently grows? Preferred habitat

Crofton Weed occurs in the humid subtropics in areas which are frost-free and have a rainfall exceeding 1500 mm per annum; often on roadsides, abandoned cultivated areas and overgrazed pastures and often to be found on sloping land (Parsons & Cuthbertson 2004). Crofton weed also occurs in temperate areas, normally in damp to riparian areas.

Are there similar species?

Crofton Weed is only likely to be confused with Mistflower, Ageratina riparia, in Australia. That species is not erect, but is a creeping or scrambling herb which is usually no more than about 40-60 cm tall. Furthermore, its stems have only a few, fine hairs while the young stems of Crofton Weed are densely covered in sticky glandular hairs. The leaves of Mistflower are narrower and elongated rather than diamond or trowel-shaped as in Crofton Weed (Navie 2004).

Why Is It A Weed?

What are its impacts?

Crofton Weed (Ageratina adenophora) is a rapid-spreading weed that has become a nuisance in many areas along the eastern coast of Australia, emerging as a weed in Victoria, South Australia and Western Australia . It is particularly invasive on cleared land that is not grazed, such as public reserves, and causes particular problems for horse owners as its poisonous to horses. Crofton weed is commonly found include: land cleared but not revegetated with pasture, roadsides and waste areas, ungrazed small holdings, state forests, national parks, abandoned banana plantations, fencelines. Once established, seedlings tolerate shade and grow rapidly. In this way, small infestations of Crofton weed rapidly increase in size unless controlled (DPI NSW 2019).

Agriculture: Crofton Weed is an aggressive weed of pastures, affecting the carrying capacity of grazing lands, and also affects crop yield. Cattle find Crofton Weed unpalatable but sheep and goats eat it without ill effect (DPI NSW 2019). It prefers wetter pastures (e.g. kikuyu grass pastures on wetter slopes), is usually not eaten by cattle, and can reduce the carrying capacity and productivity of invaded areas (Queensland Government 2016). However, it is poisonous to horses, causing acute swelling of the lungs which leads to hemorrhaging and death. In Queensland the disease is called "Tallebudgera Horse Disease" and in New South Wales it is known as "Numinbah Horse Sickness" (Parsons & Cuthbertson 2001; Land Protection 2006).

Native ecosystems: In ungrazed lands such as public reserves and native bush it reduces the ecological value of bushland (Parsons & Cuthbertson 2001; Trounce & Dyason 2003; Land Protection 2006). Crofton weed is an aggressive invader of public amenity land such as State forests, national parks and nature reserves, as well as public utility easements such as railway embankments. It it is also commonly found in urban bushland, open woodlands

Urban areas: It is also an aggressive weed on cleared areas,  and disturbed areas, examples being; creeklines, riparian areas; roadsides, parks and amenity areas and in reserves and parks in peri-urban to urban areas.

What is its history in Australia?

In the 19th century Crofton Weed was introduced widely throughout the world as an ornamental (Parsons & Cuthbertson 2001). Crofton Weed was introduced to Australia from England in about 1875, apparently being first grown in Sydney as an ornamental. It was first collected as a garden escape in Sydney in 1904. Crofton Weed was introduced as an ornamental to the north coast of New South Wales in the 1920s, soon becoming a weed of newly cleared land along the New South Wales – Queensland border and recorded as naturalised on the Springbrook plateau in 1930 (Auld & Martin 1975; Parsons & Cuthbertson 2001). A combination of drought, overgrazing and a shortage of fertiliser is believed to have been responsible for its sudden expansion between 1940 and 1950 through this region. It spread so fast that in some areas dairy farmers and banana growers abandoned their holdings (Dodd 1961; Parsons & Cuthbertson 2001).

How To Manage It?

Best practice management

Crofton weed can be controlled by chemical and no chemical means, via physical removal and mechanical management. The main control methods are slashing and mowing and chemical (herbiside) treatments when actively growing,  In Australia, despite a vigorous and sustained programme of control, Crofton Weed still persists in significant amounts in the coastal area surrounding the New South Wales and Queensland border. This may in part be due to the preference of the weed for steeply sloping frost-free land, a major factor in limiting mechanical and high volume chemical treatments, while the danger of drift onto neighbouring horticultural crops precludes aerial application of herbicides.

Chemical control: Chemical control is effective and appears to work best during late summer and autumn when weeds are actively growing (Trounce & Dyason 2003; Land Protection 2006). A combination of slashing and chemical application is often used to eradicate Crofton weed. After slashing, the weed is allowed to regrow from the crown to a height of 15–40 cm and then sprayed with herbicide. Combined with the introduction of competitive species, this strategy restores the productivity of infested land (DPI NSW 2019). Please see DPI NSW (2019) and the Australian Pesticides and Veterinary Medicines Authority for further chemical information http://www.apvma.gov.au .

Non-chemical control: Physical control: Small areas of scattered Crofton Weed plants can be physically removed with care being taken to remove roots to prevent regrowth. Small areas of scattered plants can be dug out with a mattock. Crowns must be removed to prevent regrowth.

Does it have a biological control agent?

YES

When does it grow? (lifecycle/growth calendar)

Light is essential for germination of Crofton Weed seed. More than 80% of germinations occur in February and March, with none or virtually none from July to December. Seedlings grow rapidly and are established within 8 weeks of germination. In second-year and older plants new vegetative growth begins with the first sustained summer rains and maximum growth rate occurs in late summer and autumn. Flowering commences in late August-early September with seed (fruit) produced from about early October to mid-January. Seed is produced apomictically (i.e.asexually, without fertilisation) and 15% to 30% of the healthy, 1-seeded fruit don't actually contain formed or viable seed. Despite this, in dense stands, plants may still produce as many as 60 000 viable seed per square metre. Indeed, the figure may be higher than this as it is also recorded that a single plant can produce between 10 000 and 100 000 seeds per year (Auld & Martin 1975; Parsons & Cuthbertson 2001; Trounce & Dyason 2003).

Where Is It Found?

Which states and territories is it found?

NSW, QLD, SA, VIC, WA

What areas within states and territories is it found?

Crofton Weed is most common in coastal and sub-coastal areas of south-east Queensland and central New South Wales but is also present in other parts of Queensland and New South Wales. It is recorded in South Australia (near Adelaide) and the general vicinity of Perth, Western Australia (Navie 2004). It has been recorded in Victoria.

Crofton Weed is now established in many subtropical and tropical areas of the world, including Nigeria, north-eastern India, China, south-east Asia, Pacific islands (e.g. Tahiti, Hawaii), New Zealand and Australia (Parsons & Cuthbertson 2001; PIER 2007).

Where does it originate?

Crofton Weed is native to Mexico (Auld & Medd 1992).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

NO

Where is it a declared weed?

NSW

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

Ageratina adenophora

Other scientific names (synonyms)?

• Eupatorium adenophorum Spreng.
• Eupatorium glandulosum Michx.
• Eupatorium glandulosum Kunth

Does it have other known common name(s)?

Catweed, Hemp Agrimony, Mexican Devil, Sticky Agrimony, Sticky Eupatorium.