Stachytarpheta jamaicensis (L.) Vahl, Enum. Pl. 1: 206 (1804)

Synonyms
Abena jamaicensis (L.) Hitchc.
Bouchea hyderabadensis forma monstros Wall. ex Moldenke
Stachytarpheta bogoriensis Zoll. & Moritzi
Stachytarpheta friedrichsthalii Hayek
Stachytarpheta indica var. jamaicensis (L.) Razi
Stachytarpheta jamaicensis forma albiflora Standl.
Stachytarpheta jamaicensis forma atrocoerulea Moldenke
Stachytarpheta jamaicensis var. longifolia Hiern
Stachytarpheta jamaicensis forma monstrosa Moldenke
Stachytarpheta jamaicensis forma parviflora Moldenke
Stachytarpheta mexicana Steud.
Stachytarpheta pilosiuscula Kunth
Valerianoides jamaicense (L.) Kuntze
Valerianoides jamaicense (L.) L.W. Medicus
Valerianoides jamaicense var. angustifolium Kuntze
Valerianoides jamaicense forma glabrum Kuntze
Valerianoides jamaicense var. linearifolium Kuntze
Valerianoides jamaicense var. spathulatum Kuntze
Valerianoides jamaicense forma strigosum Kuntze
Valerianoides jamaicensis (L.) Medik.
Verbena americana Mill.
Verbena jamaicensis L.
Verbena pilosiuscula (Kunth) Endl.
Zappania jamaicensis (L.) Lam.

Description
An erect perennial herb, up to 1.2(-2) m tall, sometimes woody at the base, often dichotomously branched from the base and spreading; young stems obtusely quadrangular, sparingly hairy. Leaves opposite, simple, obovate to oblong-elliptical, (2-)4-9 cm x (1-)2-5 cm, base cuneate to wing-like decurrent, apex obtuse to slightly acute, margin serrate-dentate, glabrous above, sometimes sparingly hairy below; subsessile to shortly petiolate; stipules absent. Inflorescence a spike, solitary, terete, stout, often flexuous, 15-50 cm long, rachis up to 7 mm in diameter, the furrows of the half immersed flowers much narrower than the mature rachis; peduncle (0.5-)1-2.5(-3.5) cm long, glabrous. Flowers sessile, at first erect, later immersed in the thickened rachis, bracteate; calyx compressed, completely embedded, about 5-7 mm long, the rim bilobed with 4 equal and 1 smaller tooth; corolla pale bluish, violet or purple, with a whitish spot at the throat, hypocrateriform, the tube about 1 cm long, slightly curved, 2-lipped, the upper lip 2-lobed, the lower 3-lobed, lobes subequal, the limb about 8 mm wide; fertile stamens 2, staminodes 2; ovary superior, 2-locular, style included. Fruit a schizocarp, oblong-linear, 3-5(-7) mm x 1.5-2 mm, enclosed in the fruiting calyx, splitting at maturity into 2 hard mericarps, each 1-seeded. Seed linear, without endosperm. [From PROTEA]

Ecology
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 too heavy soils with a pronounced dry season, from sea-level up to 1500 m altitude. Flowers and fruits throughout the year. Only a few flowers of a spike are open simultaneously. They are ephemerous, expanding in the early morning and falling off in the afternoon of the same day. The flowers are specialized for butterfly pollination, but other pollinators may also affect pollination. When flowers or spikes are detached the corolla is shed within a few minutes, if put in water in time new flowers will open the following morning. Seeds are easily dispersed by rainwater.

Uses
The juice of the leaves, roots or the entire plant is used in many countries as a tonic, emetic, expectorant, sudorific, stimulant, purgative, emmenagogue, emollient and cooling agent. It is used locally in various parts of its range in the treatment of headache, earache, malaria, yellow fever, syphilis, jaundice, contusions and wounds caused by blows, liver trouble, intestinal worms, and nervous pains. It is widely used in the treatment of dysentery. In Peninsular Malaysia, a decoction of the leaves is drunk against ulcers in the nose and as an antiperiodic in malaria. In Java, a decoction of the root is used for gonorrhoea and as an abortifacient. In Indo-China, the pounded leaves are rubbed on the body as a febrifuge. In West Africa the leaf sap is used in the treatment of ophthalmia and applied to sores in childrens ears; internally it is taken in the treatment of heart troubles. In Java, it is fed to cattle and horses as fodder. The young shoots are eaten as a side dish. The dried leaves are used as an adulterant in tea. Often planted as an ornamental and for hedges.

Distribution
Originates from the New World tropics, and at present has a pantropical distribution.

Local names
Cambodia: mo mi scha.
English: Blue Jamaican, Snakeweed, (bastard) vervain.
French: Queue de rat, vervaine (Fr).
Indonesia: jarong (Javanese, Sundanese), gajihan, ngadi rengga (Javanese).
Philippines: kandikandilaan (Tagalog), bolo moros (Bikol), albaka (Panay Bisaya).
Thailand: phan nguu khieo (central), yaa nuat suea (northern), yaa haang nguu (peninsular).
Vietnam: du[oo]i chu[ooj]t, h[ar]i ti[ee]n.