Good garden design involves grouping plants together so that they complement each other. In order to achieve an attractive combination you need to choose plants with different textures. This article by Kathy Woodard which I found over on The Garden Glove website explains that there are three different types of texture and how to use these in the garden.

Garden a little boring? Have no idea why? Chances are that it needs a design shake up. The basic principles of design should come into play when designing your garden, ?and using texture in the garden is one of the quickest ways to add interest and give it that ?designed? feel. What do I mean when I talk about texture in the garden, and how do you use it? There are three easy ways to utilize texture when planning, re-vamping, or just changing things up in the garden.
What is Texture in the Garden?
Texture is the combined look of all the surface elements of a garden working together, and is usually defined by being fine, medium or bold textured. Fine textured plants and elements are usually wispy and delicate, and look better in broad groups and swaths than alone. An example would be airy Queen Annes Lace. Bold texture are plants with wide, strong leaves or flowers and usually demand a lot of attention. The most common examples are hostas. Medium texture in the garden is just that? medium. Which includes just about everything else! Most plants are medium textured. ?The photo below shows all three textures working together in a garden.
How to Use Texture
The trick to using texture in the garden is to realize what you want from your space. Lots of bold texture is usually a space with much more drama and possibly formality. A space with mostly fine texture tends to be very casual, natural and free flowing. The idea is to ?find a mix that works for you. Is your garden too bold and hard looking? Add some fine texture to soften it. Too boring, as if everything is lost? Contrast fine texture with bolder plants or elements. The mix that is right for everyone is different, and I do not believe in rules in a personal garden. Part of the joy of gardening is discovering these things about your plants and your space, and working to create the feeling you want.

See more at The Garden Glove