Sharp gardening revels in spiky architectural foliage plants to create a bold structure. Flowering perennials flesh the skeleton out: thrusting spires such as kniphofias, thistle-type flowers like echinops, and globe flowers with strappy leaves – alliums and agapanthus – both echo the spear-like leaves and add contrast. Ornamental grasses with their pointed tips complete the look, their floating, feathery outlines setting off the rigidity of spiky forms.