PERENNIALS contribute detail to a planting scheme, providing low-level accents or drifts in beds and borders. If the garden designer is an artist who paints with plants, then perennials are her colour palette. Colour can transform a garden, softening hard landscaping, creating energy and different moods within it. The flower shapes of spires, globes, plumes, umbels and daisies create a varied and intricate texture constantly changing throughout the seasons. Many of my plants are chosen for their architectural form and ability to die gracefully - they wear frost well.