Quick Facts

Quick facts

  • Originally from Cape Province in South Africa and Namibia, Calomba Daisy (Oncosiphon suffruticosum) is an upright, spreading, aromatic annual herb growing to 1 m high with 100s yellow flowers.
  • A weed of disturbed areas including; degraded pastures, cultivated fields; roadsides; seasonally inundated; and waste areas.
  • Found mainly semi arid areas in Western Australia and South Australia.
  • It is a strongly aromatic plant, unpalatable to stock, with no food value.
  • Reduces the area available for grazing and significantly reduces the yield of cereal crops.
  • Calomba Daisy seeds are dispersed by wind, animals or vehicles, in gravel and soil.
  • It can be controlled with herbicides and best practice land management practices.

What Does It Look Like?

What is it?

Calomba Daisy (Oncosiphon suffruticosum) is an upright, dense multi-stemmed, spreading, aromatic, annual herb, growing to 200–600 mm tall, sometimes to 1 metre high. The first leaves form a small rosette, from which grows an upright, leafy flowering stem. The erect stems are stout, becoming woody with age, and usually un-branched below the flower head. Leaves are 20–40 mm long, and 10–20 mm wide, in outline oblanceolate (lance shaped, about 4 times as long as broad, broadest in the upper half, tapering to a narrow base), and deeply divided 2-3 times into thin lobes with the ultimate lobes (all final lobes) under 1 mm wide, grey-green, and covered with short soft hairs, without a leaf-stalk, with the base clasping the stem.

The flower-heads are yellow, in ball-shaped heads at the top of the stems, grouped into dense flat-topped terminal clusters called corymbs (many flowered inflorescence with branches starting at different points but reaching about the same height). There are numerous to a hundred flower-heads per stem, and many to a hundred or more stems per plant. Each flower head is borne on varying sized flower stalks to 10 mm long. Flower-heads are 3–5 mm diameter, with numerous tightly packed 4-lobed yellow flower (disc florets) just exceeding the surrounding involucral bracts (leaf like structures surrounding the flower-heads). These bracts are 2-seriate, oblong (length a few times greater than width, with sides almost parallel and ends rounded), 1–3 mm long, bracts sub-equal, mostly (dry and membranous), without hairs. The receptacle, the portion at the top of the stem where the flowers of the head are borne, is conical and about 1 mm diameter at maturity.

The fruits or 'seeds' (cypselas) are wedge-shaped; with straight sides converging at base, about 1–1.5 mm long, grey-brown, more-or-less 3-angled and ribbed and minutely crowned with white scales to 0.5–1 mm long (Animal and Plant Control Commission of SA 2000; Parsons & Cuthbertson 2001; Thompson 2007; VicFlora 2016).

For further information and assistance with identification of Calomba Daisy, contact the herbarium in your state or territory.

Flower colour


Growth form (weed type/habit)


Where it currently grows? Preferred habitat

Calomba Daisy occurs mainly in loose sandy soils in disturbed areas such as cultivated fields, degraded pastures, roadsides and waste areas (Parsons & Cuthbertson 2001).  It is most common on red or red/brown (gravelly) clay loams, or granite and limestone soils. Calomba daisy can also be found in seasonally inundated areas and clay pans. The areas where it may establish further are sandy mallee soils and pastoral areas (Government of South Australia 2014).

In Western Australia, it also occurs on red clay loam, red-brown gravelly clay loam, granite, limestone. Seasonally inundated areas, clay pans, paddocks, road verges. (Western Australian Herbarium 1998–).

Are there similar species?

Calomba Daisy can be distinguished from:

Globe Chamomile (Oncosiphon piluliferum) by its greater height (60 cm compared to 40 cm), longer leaves (4 cm compared to 2 cm), smaller flower heads when in full bloom (3-5 mm diameter compared to 5-8 mm), a different shaped flower head (globose but flattened on top compared to wholly globose) and a greater number of flower heads per stem (numerous to hundreds, compared to several to numerous) (Thompson 2007). Globe Chamomile, also of South African origin, occurs in south-western Western Australia (Thompson 2007). Globe chamomile (Oncosiphon piluliferum) has rounder, globe shaped flower heads whereas calomba daisy (Oncosiphon suffruticosum) has more 'club' shaped flower heads.

The genus can be distinguished from Pentzia by its habit as it is herbaceous rather than woody.

It may be distinguished from Matricaria by the different shaped flower head which is subglobose (not quite spherical) rather than ovoid (egg-shaped), and the presence of hairs on the plant (Matricaria is hairless) (Thompson 2007).

Why Is It A Weed?

What are its impacts?

Calomba Daisy (Oncosiphon suffruticosum) is primarily a weed of perennial pastures, sometimes cropping, and is also found spread along roadsides, found in disturbed, open, or bare areas including native vegetation, especially in semi arid areas.

Agriculture: Can invade and dominate perennial pastures, especially degraded or little maintained pastures, replacing and competing with more valuable pasture species for water, light and nutrients, reducing the area available for grazing. It is a strongly aromatic plant, which is unpalatable to stock and has no food value. If eaten by stock when other feed is scarce, Calomba Daisy will taint meat and milk products. In addition can invade cropping and significantly reduce the yield of cereal crops. species reducing carrying capacity (Parsons & Cuthbertson 2001). Calomba Daisy is not usually a problem in cropping rotations, as it is easily controlled by knockdown and pre-emergent herbicides. However, a late germination may reduce the yield of a stressed or uncompetitive crop. Alternatively, short crops such as field peas may be overtopped by a late germination of Calomba Daisy resulting in yield reduction (Government of South Australia 2014).

Native ecosystems: A weed of grazed arid woodlands and open areas, included degraded grassland, and near coastal, and some dune areas and observed on the edge of saltmarshes.

Urban areas: A weed of roadsides and disturbed areas around habitation.

How does it spread?

The seeds of Calomba Daisy are partially adapted for dispersal by wind but tend to remain in the flower head until this breaks up. Spread occurs when the whole flower head is broken off and moved by wind, animals or vehicles. Seeds may also be carried in fodder and produce (Parsons & Cuthbertson 2001). Most seeds germinate in the following autumn, but a small percentage of the seed will remain dormant for three years or longer (Government of South Australia 2014).

What is its history in Australia?

Calomba Daisy is thought to have been introduced to South Australia in contaminated fodder imported during the 1922 drought. It was first recorded at Calomba, north of Adelaide, in 1930-31 (Parsons & Cuthbertson 2001).

How To Manage It?

Best practice management

Calomba Daisy (Oncosiphon suffruticosum) can be controlled by herbicides, although some population are resistant to some modes of action (herbicide groups) and by hoeing when young.  As Colombia daisy thrives on bare patches, plant can be excluded by best practice management of pastures with good cover, or grazing management. Mechanically control is not normally used as plant regrow with little moisture.

Chemical control: The most cost-effective way of removing small or isolated patches of Calomba Daisy is by spot spraying. Larger areas of broadacre infestations can be controlled with  a range of herbicides selected to prevent damage to crops and pasture (Parsons & Cuthbertson 2001). Populations of Calomba Daisy in South Australia have evolved some herbicide resistance (Heap 2021). A summary on the 'International Survey of Herbicide Resistant Weeds' web site Heap (2021) states that 'Calomba Daisy first evolved resistance to Group B/2 herbicides in 2004 and infests Cereals. Group B/2 herbicides are known as ALS inhibitors (Inhibition of Acetolactate Synthase ). Research has shown that these particular biotypes are resistant to metsulfuron-methyl and they may be cross-resistant to other Group B/2 herbicides'. Please see the Australian Pesticides and Veterinary Medicines Authority for chemical information available at http://www.apvma.gov.au 

Non-chemical control: Physical control: Outliers and small infestations of Calomba Daisy can be controlled is by hoeing when young. 

Mechanical control: Slashing, mowing or grazing rarely controls this weed, as it can easily regenerate after further rain

Competition and management: Calomba Daisy will only dominate where competition is removed, therefore in semi-arid pastures, preserving pasture via appropriate stocking density, and removing small patches is the most effective control method (Government of South Australia 2014). Late cultivation provides reasonable control, and late sowing of winter growing crops offers some control on arable lands. Grazing management is inadequate for large infestations and grazing generally benefits the weed.

Does it have a biological control agent?


When does it grow? (lifecycle/growth calendar)

Most Calomba Daisy seeds germinate in autumn. The seedlings are tiny and need gaps in pasture or bare ground to establish. Plants over winter as rosettes, and then flower stems develop in August. Flowering occurs in September to December and in early summer, the plants die leaving dry woody stems with the seeds still in the flower heads (Animal and Plant Control Commission of SA 2000; Parsons & Cuthbertson 2001; Spooner 2004).

Where Is It Found?

Which states and territories is it found?


What areas within states and territories is it found?

In South Australia there are large infestations of Calomba Daisy in the central region, on the northern Adelaide Plains and the lower northern agricultural districts, especially the Hundreds of Dublin, Balaklava and Inkerman, with a large infestation and some isolated plants in the Murray Mallee, and scattered on northern Yorke Peninsula and the mid north, with a few infestations in the SA Murray Darling Basin, with isolated plants and infestations on the Eyre Peninsula and northern pastoral areas (Government of South Australia 2014). Several small roadside population have been collected from the roadside in the arid zone 500 to 800 kilometres north, to just past Cobber Pedy (AVH 2021).

In Western Australia, it occurs mainly in the Goldfields District, near Kalgoorlie and Kambalda, where it was probably introduced by rail transport from South Australia. It also occurs in the paddocks and road verges near Trayning in the Central Wheatbelt. There are isolated occurrences near Esperance, Hamelin Bay and Northam (Spooner 2004).

There are two isolated occurrences in Victoria (Parsons & Cuthbertson 2001; AVH 2021).

Where does it originate?

Calomba Daisy originates from the Cape Province in South Africa and Namibia (GRIN 2000; Thompson 2007).

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

Oncosiphon suffruticosum

Other scientific names (synonyms)?

  • Matricaria multiflora Fenzl ex Harv.
  • Matricaria suffruticosa (L.) Druce
  • Pentzia suffruticosa (L.) Hutch. & Merxm.
  • Tanacetum suffruticosum L.

Does it have other known common name(s)?

Shrubby Mayweed, Chamomile, Matricaria, Mayweed, Sheepbush, Stinking Daisy, Stinking Weed, Yellow Top, Yellow Weed, Pentzia

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