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Articles

Stachytarpheta jamaicensis (L.) Vahl

Stachytarpheta jamaicensis (L.) Vahl

Family

Verbenaceae

Synonyms

Stachytarpheta indica auct. non (L.) Vahl.

Vernacular Names

English

Snake­weed (Blue, Jamaican), vervain (Bastard).

Indonesia

Jarong (Javanese, Sun­danese), gajihan, ngadi rengga (Javanese).

Philip­pines

Kandikandilaan (Tagalog), bolo moros (Bi­kol), albaka (Panay Bisaya).

Cambodia

Mo mi scha.

Thailand

Ph an nguu khieo (Central), yaa nuat sue a (Northern), yaa haang nguu (Peninsular).

Vietnam

Du[oo]i chu[ooj]t, h[ar]i ti[ee]n.

French

Queue de rat, ver­vaine.

Geographical Distributions

Stachytarpheta ja­maicensis originates from the New World tropics, and at present has a pantropical distribution.

Description

Stachytarpheta ja­maicensis is an erect perennial herb, up to 1.2(-2) m tall which is sometimes woody at the base, often dichotomously branched from the base and spreading. The young stems are obtusely quadrangular and sparingly hairy.

The leaves are arranged opposite, simple, obovate to oblong-elliptical, measure (2-)4-9 cm x (1-)2-5 cm, wedge-shaped to wing-like decurrent at base, with apex obtuse to slightly acute, with serrate-dentate margin, hairless above but sometimes sparingly hairy below. The leaves are subses­sile to shortly-petiolate while the stipules are absent.

The inflores­cence is a spike, 15-50 cm long, solitary, cylindrical, stout and often flexuous. The rachis is up to 7 mm in diame­tre. The furrows of the half-immersed flowers are much narrower than the mature rachis. The peduncle is (0.5-)1-2.5(-3.5) cm long and hairless. The flowers are ses­sile, at first erect but later immersed in the thickened rachis. The sepal is compressed, completely embedded and about 5-7 mm long, while the petal is pale bluish, violet or purple, with a whitish spot at the throat, and saucer-shaped, with the tube about 1 cm long, slightly curved and 2-lipped. The upper lip is 2-lobed while the lower is 3-lobed. The lobes are subequal while the limb is about 8 mm wide. There are 2 fertile stamens and 2 staminodes. The ovary is superior, 2-locular with style included.

The fruit is a schizo­carp, oblong-linear, measures 3-5(-7) mm x 1.5-2 mm and is en­closed in the fruiting sepal. It splits at maturity into 2 hard mericarps where each mericarp is 1-seeded. The seed is linear and without endosperm.

Ecology / Cultivation

Stachytarpheta jamaicensis is a common weed of disturbed soils on roadsides, waste places, espe­cially in pastures but also in plantation crops throughout Asia and Oceania. The main habitat is sunny, to lightly shaded, preferably not on too heavy soils with a pronounced dry season, from sea level up to 1500 m altitude.

Line Drawing / Photograph

Stachytarpheta_jamaicensis

References

  1. Plant Resources of South-East Asia No.12(2): Medicinal and poisonous plants 2.