Seedhead
The seedhead of a plant is any ripe fruit which contains seeds, although it is often used to refer to a flowerhead which has gone to seed and retained its basic ornamental shape.
This term is, more usually, used to describe seedheads which give some extra aesthetic value. Gardeners often leave the seadheads of agapanthus, echinacea and many grasses intact for as long as possible after their flowering season, for their attractive display. One of our favourites is the swirling seedhead of the clematis, such as Clematis x durandii.