The options for building a deck trellis range from the very simple, such as hanging string or rope on which plants can climb, to more complex and decorative, such as installing wooden slats in a cross pattern from scratch. Trellis panels are also available to make the process of installing a deck trellis much easier, and a builder or homeowner must decide what material he or she wants to use for the deck trellis. Metal can be very decorative and visually appealing, but it may not be the best choice for plants. String or rope is by far the easiest trellis design, though hardly the most visually appealing.
The purpose of a deck trellis is to allow climbing plants to cling to the material and therefore climb and thrive, but some homeowners install deck trellises for shade, aesthetics, or privacy instead. Choosing the purpose of the trellis will help the builder or homeowner decide which type of trellis is best. Metals such as aluminum, steel, or even iron can be used as a deck trellis, and the visual appeal of such a trellis will be significant. Metal can, however, heat up when it is placed in direct sunlight, which means it may be harmful to some types of plants. If a homeowner wants a trellis that will be safe for plants, he or she can install an interwoven wood trellis that will allow plants to cling to it without risking burning from heat from the sun.
Wood trellis designs can block a significant amount of sunlight, however, so if a homeowner is concerned about blocking the sun from the deck, this may not be the best choice. Wood will also take some maintenance, as it is prone to rot, mold, mildew, and warping when exposed to the elements. Pressure-treated wood can help prevent such damage, but it can also harm the plants that eventually climb up the trellis. Cedar is perhaps the best choice of wood for trellises, because it is naturally resistant to damage from the elements and does not contain chemicals that may harm the plants.
A simple alternative to both wood and metal is string or rope. Tying string or rope to a high point on the deck and letting it drape down toward the plants will allow the plants to creep upward without blocking too much sunlight or heating the plants. String is not the most attractive option, however, so if aesthetics are important, one should consider another material.