Raised garden beds provide a controlled environment for any type of garden. Raised beds allow for customized soil and you can place them almost anywhere in the garden. The main requirement for a raised garden bed is proper drainage. Good drainage will keep the soil from becoming waterlogged, prevent root rot and diseases, and allow minerals and nutrients to remain in the soil. If constructed properly, drainage systems need only minor maintenance and refreshing over the years.
Plan the drainage system before constructing the bed. This will eliminate the need to create drainage in the bed later. You can incorporated drainage into the framework of the bed or on the ground the bed sits upon.
Look at the layout of the land where the raised garden bed will be placed. Marshy or waterlogged areas will require drainage to be built into the bed itself. Clay soils will also require drainage to be built into the bed. Sloping ground can have a drainage system placed under a leveled-off surface for the raised garden bed to sit on.
Level off the area where you will place the raised bed. Raised garden beds must be level for proper drainage away from all sides of the beds. Build up sloping land until it is level.
Build the structure for the raised garden bed. Make sure the bed is a minimum of 2 feet deep to allow for the drainage system to be installed. Drill 1/2-inch holes every 2 feet along each side of the structure; keep the holes staggered as they go up the side. This helps with drainage during heavy rains or snow. This will also keep the bed from building pressure on the interior and cracking or breaking.
Lay a 4-inch layer of gravel across the base of the bed. Gravel will not compact or decompose, so the bed will not sink over time. Level off the gravel layer with a rake, distributing the gravel evenly.
Measure the required length and width of chicken wire for the bed. Cut the wire with wire cutters to fit. Lay the chicken wire over top of the gravel. This will keep any material on top of the wire from settling into the gravel, while allowing drainage.
Place the soil layers over the chicken wire. Lay out a 6-inch layer of manure directly onto the chicken wire. Add a 3-inch layer of compost or mulch over the manure; use organic compost, hay or pine bark mulch for this layer. Put a 6-inch layer of topsoil over the compost. This will provide nearly 2 feet of drainage under the garden.