Garen design is the art and process of designing and creating plans for layout and planting of gardens and landscapes. Garden design may be done by the garden owner themselves, or by professionals of varying levels of experience and expertise. Most professional garden designers are trained in principles of design and in horticulture, and have an expert knowledge and experience of using plants. Some professional garden designers are also landscape architects, a more formal level of training that usually requires an advanced degree and often a state license. Many amateur gardeners also attain a high level of experience from extensive hours working in their own gardens, through casual study or Master Gardener Programs offered by the American Horticultural Society.