Built-in planters can the best idea for a small deck, especially when paired with built-in seating and kept in scale with the small size of the area. They can be clustered in a space-saving group at one side of the deck or at changes in levels to provide additional open space and improve traffic flow. A planter wall can be designed as a backrest for a bench; its cap can also double as an impromptu shelf for setting down plates and glasses. Of course, large decks can benefit from planters, too, often without the restrictions imposed by a smaller area. Large planters can be particularly useful as privacy screens when filled with tall or bushy plants or when combined with a vertical trellis.
A planter of any shape or size should be constructed from wood that's resistant to decay and retains its good looks over time. Redwood, among a handful of other species, is a popular choice for many deck projects. It's important, however, to select the proper grade of lumber for the job. Heartwood, which is cut from the center of the tree, is strong and naturally resistant to rot that can develop when wood comes in contact with water and soil. Any grade that includes "heart" in its name, such as construction heart or all-heart, is an ideal material for planters.