Start a Community Garden

Raised Bed Frames

Frames are needed to contain the new soil and keep it from washing away, to keep weeds out, and keep water from running off. The frame needs durable sides to keep the bed flat and raised 8 inches.

Frame height can vary from 4 in. to 3 ft. or more. You need at least 4 in. to assure minimum drainage and provide enough loose soil to weed, and 6 in. to grow the shortest carrots. We recommend an 8 in. bed. This height minimizes weed invasion and is the most cost efficient. Productive sweet potatoes need at least 1 ft. of depth. (An 8 in. bed can be temporarily altered by mounding soil in the center of the bed.) High drainage plants such as thyme and Irish potatoes prefer to be raised at least 18 in. For persons needing to sit high while working, such as wheel chair gardeners, 24 to 36 in. is optimum.

Frames can be made from a variety of materials, each with their advantages and disadvantages. Frames must be durable, rot-resistant, attractive, easily obtainable, inexpensive, able to hold soil, easy to weed, and non-toxic. We recommend 8 x 8 x 8 in. solid concrete blocks or 4 x 8 x 16 in. solid concrete shim blocks. Blocks are reasonably attractive, make weeding easy and permit removal for redesign. They last indefinitely and provide a convenient means for spacing plants inside the bed. Beneficial toads and ground beetles all like being around them.

We prefer solid concrete blocks to cinder blocks. They are wider and therefore more stable and easier to keep straight. You can sit on them to rest or visit. Concrete blocks have no major disadvantages except for cost and transport weight. Camp Logan Cement Works (713-869-3385) sells both solid and shim blocks. If you have a business tax number, shim blocks can be obtained for wholesale cost from White's Concrete in Pasadena. Damaged blocks may be available at no charge. Contact us for information.

Order the blocks at least a week in advance and have them delivered a few days before the garden will be built. You will also need a claw hammer or crowbar to remove the steel bands that keep the blocks on the pallet. The blocks will be delivered to the nearest accessible pavement. If this is a long way from the garden, you might consider renting equipment to move the blocks.

If you can't afford concrete blocks, we suggest inexpensive pine or recycled boards with reinforcing stakes on the outside. We do not recommend cedar, plastic or metal. Cedar costs nearly as much as concrete and is much less durable. Plastic deteriorates rapidly and while plastic wood is stable, it is more costly than concrete blocks. Metal flashing is one of several other possible frames if the garden is in a remote place or very large.

We do not recommend treated wood landscape timbers, because they leach arsenic and should not be used around food. Timbers are less durable than concrete blocks and cost the same per inch of height. If you are considering treated wood, contact Urban Harvest for more information.