Torenia crustacea

Torenia crustacea, commonly known as the Malaysian false pimpernel or brittle false pimpernel, is a species of annual or short-lived perennial flowering plant in the family Linderniaceae. Native to Asia, it has become widely distributed throughout tropical and subtropical regions worldwide and is considered a minor weed in rice paddies and other agricultural areas.

Description

Torenia crustacea is a small, prostrate to erect herb growing 5–20 centimetres (2.0–7.9 in) tall, with much-branched stems that spread widely. The stems are quadrangular (four-angled) with deep grooves and are mostly glabrous (hairless), often purplish in colour, and readily root at the nodes when in contact with moist soil.

The leaves are opposite, simple, and ovate to broadly triangular, measuring 1–2 centimetres (0.39–0.79 in) long and 0.5–1.1 centimetres (0.20–0.43 in) wide. They have short petioles up to 8 millimetres (0.31 in) long, with shallowly crenate or serrate margins and obtuse to subacute tips. The leaf surfaces are mostly hairless except for sparse hairs along the veins on the underside.

The flowers are small, approximately 1 centimetre (0.39 in) in size, borne singly in the axils of leaves or in short terminal racemes on slender pedicels 5–22 millimetres (0.20–0.87 in) long. The calyx is urn-shaped, 3–5 millimetres (0.12–0.20 in) long, with five shallow triangular-ovate lobes. The corolla is 5–8 millimetres (0.20–0.31 in) long, two-lipped, and purple with a yellow or white spot in the throat; the lower lip is three-lobed with the middle lobe larger than the others, while the upper lip is ovate and sometimes shallowly two-lobed.