An annual or short-lived perennial growing to a maximum of 2.5 metres (8.2 ft), it has erect purplish stems and rounded umbels of minuscule white or pale pink flowers in late summer.

[4] However it tolerates a range of conditions including fields, hedgerows, open woods, marshes and fens.

It has recently been determined to be an invasive weed in New Brunswick and Cape Breton, Nova Scotia, Canada.

"[5][2] The flowers are visited by a wide array of insects and are thus characterised by a generalised pollination system.

The cultivar 'Ebony', with pink flowers, has gained the Royal Horticultural Society's Award of Garden Merit.