Stachytarpheta jamaicensis



Stachytarpheta jamaicensis

(L.) Vah. 1804

pronounced: stay-key-tar-FEE-tuh juh-may-KEN-siss

(Verbenaceae — the lantana family)

common names: snakeweed, blue snakeweed, blue porterweed, Jamaica vervain

Stachytarpheta is from the Greek σταχυν (stachys), an ear of corn, and ταρφυς (tarphys), thick, referring to the thick, spiky flowers; jamaicensis means, of course, ‘from Jamaica’.
This pretty low-growing plant has colonized many of our roadsides and bush tracks, and is something of an invasive species. It blooms for much of the year, except in the driest periods, with dainty blue flowers that grow on a long, thick spike, making it an excellent nectar plant for butterflies. It also attracts humming birds. Although the plant can tolerate some salt spray, it does not do well right on the beach. It also dislikes areas of standing water, and is more prolific on the hilly slopes than on the flat land in the various bays. The flat ground in Horseshoe Bay is an exception: parts of it are very badly infected, especially in paddocks where horses have been pastured.

Snakeweed is a low, usually spreading annual or perennial herb, 60 – 120 cm tall, sometimes somewhat woody towards the base, and often purplish throughout. It has a long tap root. The stems branch dichotomously, are sparsely pubescent or glabrous, the nodes being usually sparsely pilose.

The leaves are often bluish or greyish when fresh, alternate or opposite, somewhat fleshy, elliptic to ovate, up to about 10 cm long and 4 cm wide, though usually smaller than that. The upper surface is smooth, the lower surface less so; the margins are serrate, with teeth angled forward, and the petioles anything up to 3 cm long.

The flower spikes are stout and stiff, 15 – 50 cm long, glabrous, the rachis stout and firm, up to 7 mm in diameter, the furrows conspicuously narrower than the rachis, the bracts lanceolate, 5 – 8 mm long. The calyx is completely embedded in rachis furrows, somewhat compressed, about 5 mm long. The corolla is blue to purple with a white throat, about 1 cm long. Only a few flowers on each stalk are open at any time.

The fruits are small schizocarps, 3 - 7 mm long by 1.5 - 2 mm wide, and glabrous. As they ripen, they turn dark brown, dark purple or blackish. At maturity they split into 2 mericarps.

This plant is cultivated in many places as attractive ground cover. It will grow on a very wide variety of soils, including those poor in nutrients, and is a fast grower. It prefers full sun.


Photographs taken in Picnic Bay 2009
Page last updated 7th April 2019