Decorative gardens can benefit from growing seedheads for their own sake.

Flowers With Seedheads

• The clematis family produce a variety of interesting seedheads. Shortly after flowering the above heads looked truly golden in the afternoon sunshine. The fluffy seeds will eventually be dispersed from a ball of seeds that looks just as wooly.
• Honesty is aka Lunaria after the moon shaped seedhead. After the purple flower the green seedhead, shaped like an old penny or halfacrown in old money, looses the green covering to reveal a translucent white disc and ripe seeds. Even more decorative than the flowers and they can be picked as dried flowers.
• Rosehips make some of the most startling seedheads but then again berries are all seedheads of a sort. Below is a photo of Skimmia berries the main reason for growing these small shrubs

Grasses and Other Seedheads

• The natural look from planting a range of different ornamental grasses for their seedheads has become very popular.

• Bunny Tails or Hares tail grass aka Lagurus ovatus has white fluffy seed heads on narrow hairy grey-green leaves. The seedheads can be dyed a different colour for flower arranging.
• Pampas grass is another conspicuous seedhead or you could try Pony Tails Stipa Tenuissima.
• Below is a photo of Fountain grass Pennisetum.

When the bees have done their work these pollinated thistle shaped flowers become seed shakers like pepperpots. Also a seedhead for use in a dried flower arrangement.

Even if you do not grow seedheads for their own sake think about wild life. Teasels can feed birds when other food is scarce.
Try a specialist book for more ideas Seedheads in the Garden

The Alliums below make fine seedheads after a show of globe shaped flowers. The seeds turn black and are eventually shed but you get two displays for the price of one. They would definately be on my list of plants to grow for the seed heads alone.

Honesty Lunara annua flowers deep purple and then display the penny shaped round disc seed heads. (That is the old penny not this modern contraption). As the seeds mature the discs, looking purple on the photo below, fall away to release the seeds. Trapped between the two outer disks are the seeds and a paper thin inner membrane. This membrane is white and translucent giving a winter display from these fine plants.

Other resources
Read Seed heads for display and drying.