A sustainable garden is one which is designed to be sustainable, meaning that it does not place an undue load on the environment, and may even contribute positive benefits to the natural environment. A number of criteria can be used to evaluate the sustainability of a garden, ranging from water use to the types of plants grown. In some regions, landscaping companies specialize in establishing sustainable gardens and teaching people how to maintain them, and gardeners can also create such a garden on their own.
Sustainable gardens may be ornamental, practical, or both. Vegetable gardens, for example, can include flowers which are used for natural pest control, and may be laid out in a way which is visually interesting. A sustainable garden with flowers only can be grown and managed in an environmentally friendly way, contributing benefits to the environment in addition to looking attractive.
One measure of sustainability is resource efficiency. Gardens which use less water are more environmentally friendly, as are gardens with a small carbon footprint. A gardener who goes to a nursery and buys a random assortment of plants may end up with plants shipped from remote locations, for example, which may have involved high water usage as well as fuel. Gardeners who use local nurseries and focus on local plants raised in a sustainable way are acting in a way which contributes environmental benefits.
Growing vegetables in a garden increases the sustainability, by allowing the gardener to eat close to home. For every fruit and vegetable grown in a sustainable garden, a gardener does not need to go to the store, creating a ripple effect which can be beneficial to the environment. The gardener's own energy use drops, and the gardener does not contribute to unsustainable systems by purchasing food grown in far away locations or buying food grown with chemical fertilizers and other unsustainable practices.
Some plants are considered more sustainable than others, and the same holds true for landscaping techniques. If landscaping helps retain topsoil, contributes to the heating and cooling of surrounding structures, provides shelter for wildlife, and includes native plants, it may be considered more sustainable, because the garden is benefiting the environment both directly and indirectly. Products used in the garden can also impact sustainability; using chemical fertilizers, for example, is frowned upon in a sustainable garden.
Gardeners can pick the level of sustainability they are most comfortable with, and they may start a sustainable garden from scratch, or modify an existing garden. People who promote sustainable activities often point out that every little bit counts; doing something small like replacing the washers on garden hoses to limit leaks, for example, is an important step even if a gardener does nothing else.