A Wooden Timber Raised Bed Garden
Raised beds are ideal for locations where garden space is limited and give you a head start when it comes to dealing with poor soil. Rotating the placement of different crops in a raised bed is every bit as important as it is for plants in the ground or other containers. The biggest benefit of a raised-bed garden lies in the fact that it is so much easier to maintain than traditional gardens.
Classic raised beds are made from wooden timbers. Cedar is ideal and one of the most rot-resistant natural woods available. ACQ pressure-treated lumber for ground contact is another option and will last 40 years or more. If chemical leaching is a concern, a blocking barrier of plastic placed between the timber and the soil will alleviate concerns. Studies have shown the chemicals little danger, but controversy continues and the issue is still one of concern.
Rebar and galvanized steel landscape spikes driven through the timbers will hold them in place. You can build a higher raised bed by adding additional layers of timbers on top of the first level.
In addition to materials you will need a four-foot-long spirit level, a tape measure, electric drill with long spade bits, three-pound hammer, and a utility knife.
Laying the Timber
Plan for a maximum width of four to six feet. Length doesn’t matter, but a bed that is too wide is difficult to tend without walking in it. Arrange four pieces of timber in a rectangle and measure diagonally from corner to corner. When both diagonals match in length, the rectangle has 90 degree corners.
Level the timbers with a spirit level, removing any soil from under the timber so the entire length of each timber lies flat and is also level with adjacent timbers.
Drill a hole at each end of each timber at a 20 degree angle toward the end of the timber. Recheck the measurements and then drive a piece of rebar through the holes and into the soil to a depth of at least 12 inches. The rebar will prevent the timbers from moving.
Add more timbers to raise the height, with the ends of new levels overlapping the ends of perpendicular timbers to increase stability. Flush the sides of the timbers with the timbers below.
Drill pilot holes and fasten the upper level timbers to the timbers below with landscape spikes.
Line the timbers with 6-mil-plastic sheeting using a utility knife to cut it, but do not cover the ground. Water needs a place to escape, and earthworms need to find their way in and out. You can staple the sheeting to the timbers.
Fill the bed with topsoil and compost or peat moss in layers. Mix it in with a shovel and continue adding soil and amendments until the bed is full–about six inches from the top. Heavy soils will benefit from the addition of perlite, a very light substance that helps the soil breath and improves drainage.