Quick Facts

Quick facts

  • Snakeweed (Stachytarpheta spp.) are clumping perennial shrubs that grow up to 2 m high.
  • It is a major pest of overgrazed pastures.
  • It is mainly found in coastal situations of Western Australia, the Northern Territory and Queensland.
  • It can be controlled by a combination of mechanical and chemical means.
  • It is a highly ornamental plant, contributing to its spread.

What Does It Look Like?

What is it?

Snakeweed (Stachytarpheta spp.) is a clumping perennial shrub which grows up to 2 m high from a single white woody root-stock. The stems are tough and widely branched, with opposite, lance shaped leaves up to 10 cm long and attached to the stems by short stalks (petioles). Leaf margins are crenate to serrate. The flowers are formed along stiff spikes, up to 50 cm long and 0.5 cm wide. The distinctive shape of these spikes gives these weeds their name.

Each flower is about 0.5 cm wide and has 5 petals that fuse to form a tube at their base. Flowers bloom in rotation from the bottom of the spike upwards and wilt soon after being picked. Flower colour varies with the species and may be white to pale blue, light blue, dark blue to purple or pink. A pointed bract protects the point where the flower joins the spike.

After flowering the spikes dry off and the seeds develop beneath the bracts. The seeds are dark brown to black and 4-6 mm long (Smith 1997).

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

Flower colour

Pink, Red, Purple, Blue, White

Growth form (weed type/habit)


Where it currently grows? Preferred habitat

Snakeweed prefers areas where average rainfall exceeds 1000 mm (Parsons & Cuthbertson 2001). It is reported to prefer waterways and adjacent pasture areas (Smith 1997), disturbed areas including roadsides, and over grazed pastures, and monsoon forest disturbed by pigs and buffalo (Institute of Pacific Forestry 2007) and sometimes cultivated fields (Parsons & Cuthbertson 2001).

Are there similar species?

Snakeweed (the genus Stachytarpheta) is very distinctive and not easily confused with other genera. The various species of Stachytarpheta could be confused with one another. Navie (2004) provides the following features for differentiation:

Stachytarpheta australis has pale blue or almost white coloured flowers about 5 mm in diameter that are borne on relatively robust flower spikes about 3-5 mm thick. Its stems and lower leaf surfaces are hairy an dits leaves have a somewhat wrinkled appearance with sharply toothed margins.

Stachytarpheta jamaicensis has pale blue, blue or mauve coloured flowers to 8 mm in diameter that are borne on relatively robust flower spikes 3-5 mm thick. It stems and leaves are totally hairless and its leaves are slightly fleshy in nature and sharply and deeply toothed margins.

Stachytarpheta cayennensis has dark blue, purple, or violet coloured flowers about 5 mm in diameter that are borne on slender flower spikes 1-3 mm thick. Its stems and leaves are almost totally hairless and its leaves have a wrinkled appearance with sharply, and deeply toothed margins.

Stachytarpheta mutabilis has pink to reddish coloured flowers, 10-12 mm in diameter, borne on robust flower spikes up to 7 mm thick. Its stems and both leaf surfaces are densely covered in hairs and its leaves are velvety in texture with sharply, but finely toothed margins.

These Snakeweeds are also relatively similar to common verbenas (Verbena litoralis and Verbena officinalis) and Chaff Flower (Achyranthes aspera) as these species also have very elongated flower spikes. The flowers of chaff flower are greenish-coloured and lack obvious petals and the leaves have entire margins. The verbenas have four fully developed stamens instead of the two in the Snakeweeds, and smaller flowers that are less than 4 mm in diameter.

Why Is It A Weed?

What are its impacts?

Snakeweed was included in the list of 71 species that were nominated by state and territory governments for assessment as Weeds of National Significance (WONS). Following an assessment process, Snakeweed was not included as one of the 20 WONS. However, it remains a weed of potential national significance.

Agriculture: Snakeweed becomes a problem when ground cover is eliminated or reduced such as in newly sown pastures, crops and tree plantations, or due to overstocking, and can form dense thickets. It is usually only seen when pasture is grazed down to ground level, becoming most evident in November-January. Soil disturbance such as tree clearing can allow Snakeweed to invade (Parsons & Cuthbertson 2001; Land Protection 2007).

Native ecosystems: Snakeweed can also invade disturbed areas in native vegetation where it can then dominate and exclude the establishment of native species. It can persist in shaded areas such as monsoon forest fringes and creek lines (Smith 2002).

How does it spread?

Snakeweed can be spread intentionally as ornamental plants, where they are used as hedges and ornamentals. The seeds are dispersed by vehicles, by the movement of soil, in hay and soil and are perhaps spread in contaminated pasture seed, in refuse from gardens and by rainwater. In Queensland seed has been spread in fodder, hay and in contaminated pasture seed (Smith 1997).

What is its history in Australia?

Many of the Snakeweed species have been introduced either accidentally or intentionally as garden plants from where they have spread and become a serious weed along coastal Queensland (Parsons & Cuthbertson 2001; Land Protection 2007).

How To Manage It?

Best practice management

Chemical control: Snakeweed is controlled by herbicides applied in the active growing season. The QLD DAF provide information for specific herbicides that can be used on Snakeweed (https://www.daf.qld.gov.au/__data/assets/pdf_file/0005/54392/snakeweed.pdf).

Non-chemical control: Land management: Because it only becomes a problem when pastures are overgrazed it is recommended that paddocks are destocked where Snakeweed is a problem, and then promote pasture growth.

Manual control: Small infestations can be removed manually preferably before the seeds form, as the seeds of these weeds can stay dormant in the soil for a long period of time. Larger infestations can be controlled by slashing and spraying (Smith 1997; Land Protection 2007).

Does it have a biological control agent?


When does it grow? (lifecycle/growth calendar)

Snakeweed seeds germinate at any time of the year provided moisture is available, but mainly after the first summer rains. Young plants grow rapidly and flower in late the summer of their first growth season. Plants are evergreen, making most growth in the summer wet season. Once fully established, new stems are produced continually and plants flower and set seed all year, but at a reduced rate during the dry winter (Parsons & Cuthbertson 2001; Smith 2002).

Where Is It Found?

Which states and territories is it found?


What areas within states and territories is it found?

Snakeweed is mainly found in coastal northern and eastern Australia, in Western Australia, the Northern Territory and Queensland (Navie 2004; Weeds Australia undated).

Where does it originate?

Snakeweed belongs to a group of plants that evolved in the tropical region of the American continent. Seven or eight species of Snakeweed have since become problems in tropical areas around the Pacific (Smith 1997).

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

Stachytarpheta spp.

Other scientific names (synonyms)?


Does it have other known common name(s)?

Blue Rat's Tail, Brazilian Tea, Cayenne Snakeweed, Cayenne Vervain, Dark Blue Snakeweed, False Verbena, Nettleleaf Velvetberry, Rough-leaved False Vervain, Vervain, Bastard Vervain, Blue Porterweed, Blue Snakeweed, Jamaica Vervain, Jamaican Snakeweed, Joee, Light Blue Snakeweed, Nettleleaf Vervain, Changeable Velvetberry, Pink Rat Tail, Pink Snakeweed

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