Raised bed vegetable gardening is popular because the beds can be more accessible.
They provide for less stooping, supply a solution for poorly drained sites, allow the soil to be amended easily to give better growing conditions, and may be placed in small spaces. The produce harvested would add more servings of vegetables to a meal and help stretch the dollars budgeted for food.
Beds are usually raised at least 6 to 8 inches from the surface. It may be higher if it makes it more accessible for harvesting and removing weeds. A frame to support the soil may be constructed of wood, stone, concrete block, brick or recycled plastic boards, or soil may be mounded without a rigid structure.
Bed sizes vary. They are typically constructed no more than 4 feet wide since this allows for easy reaching into the bed from either side. By not walking in the beds, soil compaction is avoided, which allows plants to grow better. Maintaining an aisle of 2 to 4 feet between beds allows easy access with tools, hose reels, chairs or wheelchairs.
Full sun is the best location for vegetable garden. However, many vegetables will produce a good crop with 4 to 6 hours of direct sunlight a day. Locate a bed away from trees if possible so that the roots will not grow into the bed and compete with the vegetables for water and nutrients. Do not place gardens near black walnut (Juglans nigra) trees since walnuts produce a compound in their roots, shoots and leaves that is toxic to many plants, including several vegetables.
To make life easier, locate your beds where water is readily available since raised beds dry out quickly and require more frequent watering than conventional gardens.
In preparing soil for the bed, adding components such as organic matter and porous material will improve soil structure. An ideal soil for raised beds consists of equal volumes of good garden soil, organic matter such as compost, peat moss, and porous material like vermiculite or perlite. If good garden soil is not available, substitute additional organic matter. Add lime and fertilizer as recommended by a soil test of the finished soil mix. In the absence of a soil test, 1 to 2 pounds of a complete fertilizer such as 10-20-10 per 100 square feet is usually adequate.
There are several ways to plant your bed. You may choose to plant in rows within the bed, or simply group similar plants together by maturation time or height. Keep in mind that diversity in plants will promote a more stable ecosystem. Monoculture, or grouping together of the same or closely related crops, may encourage more pest and disease issues. Plant diversity tends to encourage more beneficial insects and microorganisms in the planting area. You may even want to include a few flowers in your garden to increase the diversity of plants being grown.
Plan to intensively garden the space to produce more vegetables. Cool-season vegetables such as spinach, lettuce, cabbage and broccoli can be replaced after harvesting with warm-season vegetables such as tomatoes, beans, peppers, squash and corn. Then cool-season vegetables can be planted again in the fall. Another way to garden intensively is to train plants vertically when possible.
Remember that it is a good practice to move plants around if your gardening space allows. For example, if you have multiple beds, don’t grow tomatoes and related crops like potatoes, peppers and eggplant in the same bed for more than two or three years
. Give the soil a break from tomatoes and related crops for a couple of years by moving them to another bed, growing them in containers or not growing them at all. This will prevent soil pests from building up to high numbers that will eventually impact the performance of your plants.
Remember that raised beds may dry out faster than conventional gardens. A layer of mulch will reduce weed growth and water loss. A 1- to 2-inch layer of organic mulch such as compost, straw or grass clippings will slowly break down and contribute organic matter to the soil. A few layers of newspaper beneath organic mulch will help to prevent weed germination.
At least 1 inch of rainfall or supplemental irrigation per week is best. If supplemental irrigation is applied, it is best to use drip or soaker hose irrigation since these tend to direct water to the root system and not onto the plant itself.
Watering the entire plant, especially late in the evening, allows water to remain on the foliage for several hours. In certain instances, this may promote disease problems. Therefore, it is best to water in the morning if it is necessary to use some type of sprinkler that wets the entire plant.
The following workshops will be held at the OSU Extension Center, 930 N Portland, and are free and open to the public. Questions? Call 713-1125.