Stachytarpheta mutabilis

pink snakeweed


Stachytarpheta mutabilis

(Jacq.) Vahl 1804

pronounced: stay-key-tar-FEE-tuh mew-TAH-bih-liss

(Verbenaceae — the hibiscus family)


common names: pink snakeweed, pink porterweed

Stachytarpheta is from the Greek σταχυς (stachys), an ear of corn, and ταρφυς (tarphys), thick, referring to the thick, spiky flowers; mutabilis is Latin for ‘variable’.

This plant is nowhere nearly as common on Magnetic Island as is its cousin the blue snakeweed – indeed, I have seen it only occasionally. The plant photographed was growing in a roadside ditch. Pink snakeweed is native to Mexico, the Caribbean, and tropical South America; it has become naturalized in parts of northern, central and south-eastern Queensland, especially in the wet, cool areas around Kuranda and the Atherton Tableland, and possibly also in the northern parts of the Northern Territory. It is a robust species that can reach a height of 2 m and the same width. This is a weed of roadsides, waste ground and pastures, as well as sugar cane.

All of the porterweeds are clumping perennial plants with rather tough branched stems, tending towards being square in cross-section, and woody roots. They were introduced to Australia as garden plants, and have escaped to become weeds. Four varieties are found in Queensland, varying in flower colour and leaf shape, and some hybridization has also been reported. Leaves are in pairs along the stem. They are about 10 cm long and more-or-less oval shaped, and, in the pink porterweed, toothed along the edges, with the teeth pointing towards the tip of the leaf, and the leaves taper at the base into a short stalk. They are smooth on the upper surface, but have short hairs beneath.

The Pink Porterweed has the showiest flowers of the genus. The flowers open first from the base of each inflorescence and proceed upwards, one to several emerging each day between the scales on the inflorescence. As the individual flowers die, they usually remain on the plant, with the seeds produced inside them.

The flowers attract hummingbirds and butterflies.


Photographs taken at Picnic Bay 2012
Page last updated 8th April 2019