Short to medium hairy plant, overwintering by leafy rosettes, stems erect, rather robust. Leaves mostly opposite or whorled, oblong to linear lanceolate, scarcely stalked, slightly toothed, not clasping the stem. Flowers pale purplish pink, small 7 to 12 mm, in a lax raceme, stigma four lobed.

Great Willowherb is a similar but larger plant, with larger and pinker flowers. The four-lobed stigma of Hoary Willowherb is also diagnostic, but can appear club-shaped if the lobes are pressed together.

Prefers damp places on limey soils.

Damp ground, marshy areas, and water margins.

Perennial.

Fairly frequent throughout much of Britain though scarcer in the north.

Fairly common in Leicestershire and Rutland. In the 1979 Flora survey of Leicestershire it was found in 385 of the 617 tetrads.