Raised Bed Gardening

Richard Englund
Adams County Master Gardner

Several changes are being made at the Trial Gardens at the Ag Center on Old Harrisburg Rd. The most obvious is the raising of the beds in the Trial Gardens. Half of them have been raised this year with the remaining slated to be completed next year.

Gardening in raised beds, a common practice in America since colonial times, is enjoying a resurgence of popularity among home growers whether it is for raising vegetables, flowers or even some fruits such as strawberries and raspberries. There are a number of reasons to have raised beds, including poor under soil, limited space, drainage, low sections prone to ponding and ease of working. Our problem at the Ag Center was drainage. The ground there slopes just enough to encourage washouts during heavy thunderstorms.

The "raised" part means that the soil level in the bed is higher than the surrounding soil, and "bed" implies a size small enough to work without actually stepping into the bed. The bed should be no wider than 4 feet, but length can be whatever suits the site or the gardenerís needs. Wider beds can be subdivided into sections accessible from planks or stepping stones. The bed does not have to be enclosed or framed. If unframed, the use of power tillers is feasible. However, framing offers several other opportunities and a properly maintained bed will not need power cultivation.

Perhaps the most important advantage of a raised bed is more production per square foot of garden. In a traditional, straight-rows garden, good management may yield about 0.6 pounds of vegetables per square foot. Production over three years in a raised bed at Dawes Arboretum in Ohio has averaged 1.24 pounds per square foot, more than double the conventional yield. In my own garden I raise potatoes in an 8 foot by 12 foot bed and consistently get two bushels or more each year. Raised beds do not require the usual space between rows because no walking is done in the beds to cultivate during the growing season. Vegetables are planted in beds at higher densities - ideally spaced just far enough apart to avoid crowding but close enough to shade weeds.

Another reason for greater production in a given space is the improvement of soil conditions. Soil compaction can reduce crop yields up to 50 percent. Water, air and roots all have difficulty moving through soil compressed by tractors, tillers or human feet.

Raised beds also help with water conservation since you are able to water only the area that is actually growing the crops. No need to water the paths and the area between rows as is done in most gardens. There are several watering systems that ensure the water gets only where it is needed. Canvas soaker hoses, perforated plastic sprinkle hoses and drip-type irrigation disperse water in a long, narrow pattern well suited to raised beds.

There are only a few guidelines to remember in raised bed construction: Keep the beds narrow and match their length to the site and the watering system. A north-south orientation is best for low-growing crops, allowing direct sunlight to both sides of the bed. Beds that will contain taller crops such as pole beans, trellised peas or caged tomatoes might do better on an east-west axis with the lower-growing crops planted on the south side of the bed to take advantage of the sun.

The advantages of raised beds are many. Beds elevated 2 feet or more offer the promise of gardening without bending and can have benches built on the side for even more convenience. Because a raised bed warms up quicker than the surrounding ground, it can easily double as a cold frame by covering it with a lightweight clear plastic cover. Imagine being able to start plants early in covered beds and never having to transplant them.

Yes, raised beds are enjoying a resurgence of popularity. Why not think about them for your own home.

Read other articles on garden and landscape design

Read other articles by Richard Englund