Quick Facts

Quick facts

• Pacific False Buttonweed (Spermacoce exilis) is a poorly known introduced species, currently known from Christmas Island, and North Queensland.
• It grows along the ground as a spreading annual herb up to 30 cm long.
• The flowers of Pacific False Buttonweed are tiny and white or purplish-white in colour.
• It is widely naturalised throughout the tropics.
• Pacific False Buttonweed invades tracks in primary rainforest, rice, banana, sugarcane, and pinto peanut plantations, gardens, lawns and roadsides.
• There is currently no information available about control.

What Does It Look Like?

What is it?

Pacific False Buttonweed (Spermacoce exilis) [as Spermacoce mauritiana] is an annual herb. The leaves are usually in opposite pairs along the stems, are egg-shaped, 5–25 mm long and 2–10 mm across. The flowers are found in the forks of the leaves in small, dense clusters.

The flowers are tiny and usually white or occasionally purplish-white. The calyx has two lobes ca. 0.5 mm long. The corolla is a white or purple tube ca. 0.5 mm long.

The fruit is a capsule with nearly parallel sides about 1 mm long. The seeds are minute, 0.7–1 mm long, and 0.3–0.35 mm across and are chestnut brown or yellowish brown (Verdcourt 1989; Wagner et al. 1990; Burger & Taylor 1993; Ridsdale 1998).

For further information and assistance with identification of Pacific False Buttonweed contact the Herbarium in your state or territory.

Flower colour

White

Growth form (weed type/habit)

Herb

Where it currently grows? Preferred habitat

In Queensland, Pacific False Buttonweed has been collected from a range of different habitats, mostly from disturbed sites, such as farms and roadsides, but it has also invaded areas of native vegetation. It has invaded both dry and moist habitats, and a range of soil types, including sandy, granitic, loamy and red-yellow clay soil (Queensland Herbarium 2007). On Christmas Island Pacific False Buttonweed occurs along shaded tracks in tall rainforest (Du Puy 1993).

Are there similar species?

Worldwide there are approximately 275 species of Spermacoce, with approximately 90 species in Australia.

Generally, Pacific False Buttonweed can be distinguished from other species of Spermacoce in Australia by the fact that the flower clusters are found in the forks of the leaves and there are 2 calyx lobes (outermost 'petals' of the flowers), with most species in Australia having a 4-lobed calyx. There is one species Spermacoce verticillata, which also has a 2-lobed calyx and is hard to distinguish from Pacific False Button weed (Taylor & Steyermark 2004; Harwood & Dessein 2005). For further identification assistance should be sought from the Herbarium in your state or territory.

The Pacific False Buttonweed also closely resembles Spermacoce ocymoides however this species does not occur in Australia (Ridsdale 1998).

Why Is It A Weed?

What are its impacts?

Agriculture and native ecosystems: There is very little published information about the environmental and economic impacts of Pacific False Buttonweed. In Australia, although it invades tracks in primary rainforest, rice, banana, sugarcane, and pinto peanut plantations, as well as gardens, lawns and roadsides (Du Puy 1993; Northern Territory Government 2006; Queensland Herbarium 2007), there is virtually no information about the level of impact that it may have.

The government of Northern Territory, where Pacific False Buttonweed has not as yet been recorded as naturalised (Kerrigan & Albrecht 2007), perceives the species as posing a significant threat, and as such it has been declared as a noxious weed (Northern Territory Government 2007).

How does it spread?

The seeds of Pacific False Buttonweed are dispersed by water and human activities (Waterhouse & Mitchell 1998).

What is its history in Australia?

The earliest record of Pacific False Buttonweed in Australia is from Lockerbie Scrub in the Cape York area of Queensland, collected in 1990 (Queensland Herbarium 2007). It is not known how it arrived in Australia.

How To Manage It?

Best practice management

There is no published information on the control of Pacific False Buttonweed.

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

Does it have a biological control agent?

NO

When does it grow? (lifecycle/growth calendar)

In North Queensland flowering specimens of Pacific False Buttonweed have been collected in February, November, May and July (Queensland Herbarium 2007). In the Northern Territory Spermacoce species generally flower and fruit from December to May, spanning the wet season and the early part of the dry season, although some species can be found flowering and fruiting at other times of year (Harwood & Dessein 2005).

Where Is It Found?

Which states and territories is it found?

QLD

What areas within states and territories is it found?

In Australia, the Pacific False Buttonweed is currently known from the Cook and the North Kennedy regions of North Queensland (AVH 2007; Queensland Herbarium 2007), and from Christmas Island (Du Puy 1993).

Where does it originate?

Pacific False Buttonweed is probably of American origin (Smith & Darwin 1988; Ridsdale 1998; Taylor & Steyermark 2004) although some sources suggest the species may have originated from Africa and Malesia (Wagner et al. 1990). Pacific False Buttonweed is today distributed in tropical Africa, tropical Asia, North America (Mexico), the Pacific (Samoa, Solomon Islands) and tropical South America although it is widely naturalised in other areas, the exact distribution being obscure (GRIN 2007).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

NO

Where is it a declared weed?

NT

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

Spermacoce exilis

Other scientific names (synonyms)?

• Borreria exilis L.O.Williams
• Spermacoce mauritiana Gideon