It is a herbaceous (non-woody) perennial speedwell that produces a creeping stem that roots at its nodes then ascends to flower, to 60 cm (24 in) in length, using other vegetation as a scaffold.

The paired leaves alternate in direction and are very narrow and pointed, stalkless, somewhat rigid, often with a yellowed or reddened hue, with obscure teeth (or none), and curling under at the edges; it initially rises with its leaves vertical to push through vegetation and later opens them sideways to anchor its position.

The flowers are small (3–7 mm (0.12–0.28 in) diam), pale lilac, pale blue or whitish, although sometimes strongly coloured, with accentuated veins, which at maturity form flat capsules 3–5 mm long, deeply divided at the top.

scutella), some forms are densely hairy usually with a mixture of glandular and non-glandular hairs, especially in drier habitats (var.

[1] Its habitat is marshes, shores, water banks and a wide range of other wet places, particularly acidic.