Verbena Bonariensis (Purpletop Vervain)

A tall herbaceous perennial with erect, branching stems to 2m in height, bearing sparse, oblong leaves. Numerous branched clusters of small, lilac-purple flowers appear from summer to autumn; these are a good nectar source for pollinating insects. Cut down in spring as new growth emerges from the base; deadhead in autumn if seed is not required.