Base Material for Square Foot Gardening

Building on Concrete

• If the only space you have for a raised bed is on an existing hard surface such as a concrete patio or driveway, you'll need a solid surface for the base to prevent soil from crumbling out the bottom of the raised bed. A solid piece of 5/8-inch or 3/4-inch plywood nailed to the bottom of the raised bed and then drilled for drainage holes makes an ideal base. The same base works for beds that are raised above ground on sawhorses for gardeners who have difficulty bending down to soil level.

Building on Soft Areas

• If you're building your square foot garden on an existing flower bed or lawn, use cardboard or a thick layer of newspaper as your base. The cardboard or newspaper suppresses weeds and kills any grass under the bed. This prevents these unwanted plants from competing for water and nutrients with the vegetables and flowers you plant. The base material should extend at least a foot beyond all sides of the bed. After the bed is in place, cover the excess base material with mulch or pea gravel to create a walkway around the bed.

Choosing Your Site

• The site for your square foot garden should receive at least six hours of sun each day, especially if your goal is to grow vegetables. Although it's best to place your raised beds on a level surface, if your garden space is on a slight slope you can level the bed with boards or stones. For convenience, your square foot garden should be near a hose or other water source.

Filling Your Beds

• Filling your beds with the right type of material will get your square foot garden off to the best start possible. The Square Foot Gardening website recommends a blend of one-third compost, one-third peat moss and one-third vermiculite. If you don't want to mix your own, you can purchase potting mix. Choose one that is specially formulated for vegetables or opt for a standard soilless potting mix. Do not fill your beds with topsoil because it doesn't contain the nutrients your plants need and offers poor drainage.