A raised garden bed is an above-ground, open-bottomed container filled with a rich mix of topsoil, compost and other organic materials. A raised garden bed is also the solution to many of the shortcomings of home gardening.
A raised bed is easy to build and even easier to maintain. It’s ideal for a small planting area with poor soil. It can provide for a longer growing season. It’ll produce few weeds. It can deliver a high flower and vegetable yield. It contains a rich, rock-free and loose soil that’s easy to work — even after a long, cold winter. There’s excellent soil drainage and no erosion. A simple drip system or soaker hose is all that’s needed for irrigation. There are few pests such as snails and slugs. And, if the bed is built high enough, there’s no bending over.
A raised garden bed’s soil can dry out quickly on hot summer days. The container can initially be expensive to build. The roots of nearby plants and trees may eventually invade the bed’s nutrient rich soil. And cats have been known to gleefully substitute their litter box for the raised bed’s fluffy soil.
The container of a raised garden bed can be made from wood, concrete blocks or rocks. The base should be set about six inches below ground level.
For wood containers, keep in mind that regular, pressure-treated lumber contains a mixture of chemicals to prevent rotting. Although pressure-treated wood is certified as safe for organic growing, there are also a variety of eco-friendly alternatives.
Many gardeners avoid using railroad ties because the wood may be treated with a mix of creosote and chemicals. More expensive woods, such as cedar, contain natural oils which prevent rotting and make them much more durable. Using thicker boards can also help make the box last longer.
A typical raised bed container can be from 6 inches to 4 feet high, about 3 or 4 feet wide and run as long as space permits. Build it so that you can reach every part of the bed without having to stand or lean on the soil. Avoid compacting the soil.
For best results the long side of the bed should face south, providing the most even sun exposure. Fill the bed with soil to within an inch of the top of the planter box and water with a fine spray. This will help settle the soil. Later on you can top off the planter with more soil or add a thick layer of organic mulch such as straw, grass clippings, leaves or wood chips. This will help reduce weeds and keep the soil moist.
If your yard is blessed with furry burrowing pests, such as gophers and moles, put a layer of hardware cloth (wire that’s sturdier than chicken wire) across the bottom and up about three inches on the sides before the soil is added.
After a couple of growing seasons the soil will likely have settled and the nutrients depleted. Simply add a few more inches of compost or composted manure and loosen the soil with a garden fork. Or, try a cover crop such as fava beans over the winter, to refresh nitrogen levels in the soil.
For a greater yield, plant vegetables in geometric patterns (spaced much closer together than in conventional row gardening) so that when fully grown the leaves barely touch. This gives much more usable space than conventional row gardening and it helps choke out the weeds.
For more information about building and maintaining garden beds, plan to attend Saturday’s free Master Gardener seminar on Raised Bed Gardening. Master Gardener Eve Keener will explain the benefits of raised bed gardening, how to build the beds, what materials to use and how to maintain them for long-term bounty. The Aug. 24 class is from 9 a.m. to noon at the Veterans Memorial Building, 130 Placerville Drive in Placerville.
Master Gardeners are available to answer home gardening questions Tuesday through Friday, 9 a.m. to noon by calling 530-621-5512. Walk-ins are welcome at 311 Fair Lane in Placerville.
For more information about the public education classes and activities go to the Master Gardener Website at ucanr.edu/sites/EDC_Master_Gardeners/. Sign up to receive the online notices and e-newsletter at ucanr.edu/mgenews/. Master Gardeners is also on Facebook.