The beds should be no more than 4 feet wide, but can be as long as the site or gardener needs. Wider beds can be subdivided into sections accessible by planks or stepping stones.
The bed does not have to be enclosed or framed, but a power cultivator can be used if there is no frame. However, frames also offer other opportunities; a well-maintained bed requires no skill.
Benefits of raised bed gardening include improved soil conditions; ease of work and pest control, and water conservation. Soil compaction can reduce crop yields by up to 50%. Water, air and roots have a hard time moving through soil compressed by tractors, tillers or foot traffic.
Raised beds can also help in cases where compaction is not the only problem. Due to poor drainage or excessive erosion from runoff, homeowners may encounter low-lying areas that are not suitable for traditional gardens.
There are a few guiding principles to keep in mind when building a raised bed:
Keep the bed narrow and match its length to the site and watering system.
A north-south orientation is best for growing low crops, allowing direct sunlight to the sides of the bed.
Seedbeds containing taller crops such as lentils, trellis peas, or caged tomatoes may perform better on the east-west axis. Therefore, lower growing crops can be planted on the south side of the bed and still get full sun.
Avoid creosote or pentachlorophenol treated wood for bed frames. These chemicals leach out and harm the plants. Use redwood, cedar, cement block or brick, or recycled plastic.
The soil depth should be at least 6 inches. Fill the bed with topsoil mixed with 2 to 3 inches of compost.
