The loose soil in raised beds produces higher yields.

Are Stacked Concrete Blocks Suitable for Vegetable Beds?

by Lynn Doxon

Raised beds make growing vegetables easy. You don't have to get on your knees to care for the plants and it allows you to use high-quality soil, rather than the soil you have in your yard. Raised beds eliminate drainage problems and you can extend the growing season. Concrete block beds are simple to build but have both advantages and disadvantage compared with other materials.

Advantages of Concrete Bock

Concrete blocks promote better drainage than wood beds because water can drain through the spaces between blocks. They also hold heat, warming the soil so seeds sprout more quickly and the gardening season is longer. A concrete block bed is also easier to build and doesn't require power tools. Concrete blocks do not have any toxic preservatives so they're a good choice for organic gardening.

Disadvantages of Concrete Block

Concrete blocks are generally more expensive than wood, unless you have leftover blocks from another project or recycled blocks. The site must be level for the block walls to be stable and the blocks will become misaligned over time if you don't anchor them. In dry climates, the increased drainage can be a disadvantage because it's harder to keep the well-draining soil moist. Some people also consider concrete blocks less attractive than other building materials. Decorative blocks make attractive beds but are even more expensive.

Building a Concrete Block Bed

Lay out a rectangle of blocks, no more than 4 feet wide and as long as you like, on a level surface. Use string as a guide to make the sides straight and the corners square. Place a second layer of blocks on top of the first, offsetting the blocks so the joints do not overlap. Pound 36 inch long sections of 1/2 inch rebar into the openings in the blocks to anchor them. Pound the rebar in until it is just even with the top of the blocks.

Depth of Bed

Block walls less than 2 feet tall can be laid in place without mortar or footings. If you have to use mortar and footings, wall construction is considerably more complicated. A deep raised bed also requires a great deal of soil. Few vegetables need more than 16 to 18 inches of soil and some need only 3 inches. To be accessible to people with physical limitations, beds may need to be higher than 2 feet. Otherwise, one or two layers of 8-inch blocks should be enough.

About the Author

Lynn Doxon has a Ph.D. in horticulture, is a retired cooperative extension specialist and teaches courses in urban farming. She is the author of three books: "The Alcohol Fuel Handbook," "High Desert Yards and Gardens" and "Rainbows from Heaven." Doxon wrote the Yard and Garden column for the "Albuquerque Journal" and numerous magazine and newspaper articles and cooperative extension service guides.

Photo Credits

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