Thomas J. Story
Thanks to a recently developed building material--composite lumber, designed for decking--you can build rotproof raised beds. The triangular bed shown here is made with Trex, a composite of recycled plastic bags and wood fibers (Trex; 800/289-8739 or www.trex.com). Trex comes in 52-inch 4-by-4s for posts (available soon) and 2-by-6s for sides and tops. If you need rectangular planters, you can modify this design.
It's heavy, so build the planter in sections that can be screwed together on-site.
If the planter is no more than three boards high (about 16 inches tall) and the site is flat, the posts can just rest on the ground (as shown here). You'll need longer posts for in-ground installations.
Assemble with screws. If you are using standard deck screws, drill the holes first, since composite lumber is dense and hard. A self-drilling deck screw, designed for working with products such as Trex, is available; it's called Fastap Poly² (800/847-4714 or www.fastapscrews.com). Use 3-inch-long screws.