Gardens that Last for Years

Gardens that Last for Years
Raised Beds with Rubber Lumber, a Technique that Works!

For thousands of years, the Chinese have realized the benefits of gardening with raised beds. Improved drainage, higher yields, an extended growing season, no soil compaction, easier working and harvesting - all to be had with a simple, age-old technique.

Promoters of the raised bed gardening concept have taken the idea a step further for home and commercial gardeners alike, with the use of new-generation materials to construct the beds.

Top among the list of such materials for Steve Upson, a horticulturist with the nonprofit consultation and research-oriented Samuel Roberts Noble Foundation in Ardmore, Okla., is the use of recycled auto tires converted to rubber lumber.

"Tires are readily available and in many ways are ideal for raised bed construction," Upson said. "The Environmental Protection Agency estimates a tire a year is discarded for every man, woman and child in the country - more than 250 million! United States residents throw away enough tires each year to more than circle the globe."

Upson, who has been experimenting with raised bed gardening for nine years, said this availability is one reason tires are such a good source for bed construction. Another is the longevity of the rubber, but he adds building rubber lumber isn't for everyone - besides needing a supply of tires, the gardener must have tools and time, and be able to invest sweat equity into the project. The good news is that if built primarily from materials already on hand or free for the taking, a rubber-board raised bed can cost a third of the price of a treated lumber bed; or about 30 cents per foot of bed length.

The benefits of rubber-board raised beds are numerous, according to Upson. After construction, gardeners can grow a variety of produce, from traditional vegetables to miniature fruit trees to flowers.

Types of Rubber Board Beds
After several years of field research at the Noble Foundation Horticulture Center, Upson and coworkers have developed three types of raised beds made of rubber boards - the multiple-, double- and single-tire board designs.

Each of the designs has advantages and disadvantages, but it's the multiple rubber board design that Upson recommends most.

"More bed can be constructed per tire in the multiple board design than with the other two options," Upson said. "This makes it even less expensive than the others to build."

Besides costing less, another advantage of the multiple rubber board bed is that it doesn't require wood stakes for bed assembly - long-lasting rebar stakes are used instead. The disadvantage, Upson said, is that rubber boards can be heavy and difficult to handle, depending on their length.

Building Rubber Lumber for a Multiple Tire Board Bed
Materials needed
Hardware: 7/8th-inch No. 10 Phillips head sheet metal screws (two per foot of board).
Tools: Jigsaw equipped with rubber-cutting and steel-cutting blades, power hacksaw, hand drill equipped with a Phillips bit, hand grinder, eye protection (goggles), tape measure, and vinyl knife for initiating cut in sidewalls.
Tires: Approximately six tires are needed to build a 30-foot rubber board.

The procedure
This procedure allows the construction of boards of any length, short or long. However, boards longer than 30 feet are not recommended due to their excessive weight and bulk. Build boards out of tires having similar tread width.

To construct each board, follow these steps:

Remove the sidewalls using a power hacksaw or jigsaw equipped with a steel-cutting blade. This produces sections of tread 5 to 7 feet long and 6 to 8 inches in width.
Arrange the cut sections end-to-end along a work bench the length of the board to be constructed, tread down. Working from one end of the board to the other, slide the second section under the first 6 inches and secure with four sheet metal screws. Place the screws at least 1 inch from the edges of the treads to provide adequate strength. Adjust the length of the last section by cutting or by overlapping the excess with the previous section.
Form a tight loop at both ends. Secure with at least two sheet metal screws. The loops need to be large enough to hold a piece of 5/8th-inch diameter rebar.
Cut additional 6-inch-wide pieces of rubber from sections of tread. Space these pieces of rubber along the board at 18-inch centers, tread facing up. Secure each piece with two screws an inch from the left and right edges, midway between top and bottom. These "pockets" will hold rebar stakes, which will keep the board erect and anchored to the ground.
When the board is finished, turn it over and remove protruding screw points with a grinder.

Multiple Tire Bed Construction
Materials needed
Hardware: 3/8th-inch by 18-inch* rebar stakes (one for every 18 inches of border), 5/8th-inch by 36-inch* rebar stakes (four per bed), and 5/8th-inch by 10-inch rebar rod for use with sling. (*May vary, depending on soil type.)
Tools: Power hacksaw or chop saw for preparing stakes, sledge hammer, hand winch, wire sling, string line, shovel, garden rake, carpenter's level, safety glasses, and tape measure.

The Procedure

Level the garden plot.
Form a taut string line between two stakes.
Every 3 feet along the string, drive a pair of 3/8th-inch rebar stakes a half inch on both sides of the string. Drive the rebar only a few inches into the soil, as they'll be removed later. These will cradle the rubber board, holding it upright until it is secured.
Place a board between the cradles, pockets oriented opposite the bed interior, positioning one end of the board at the end of the plot. Drive a 5/8th-inch rebar stake through the loop.
Use a hand winch attached to the loose end of the board by means of a sling to stretch it. While the board is under tension, remove the cradle stakes and insert them into the pockets, driving them flush with the top of the board.
Remove the sling and drive a 5/8th-inch rebar stake through the loop.
Align the opposite rubber board parallel to the first, the distance determined by the desired width of the bed.
Use two additional pieces of cut tread to form the end pieces.
Fill with growing mixture.

"These rubber board raised beds should give gardeners years of continuous enjoyment and harvests, whether they're planting vegetables, herbs, miniature trees, or flowers," Upson said. "Besides building garden beds from some of the most durable materials available, gardeners can be satisfied knowing they constructed a bed that helps alleviate the national problem of discarded tires."

"This type of bed has met and exceeded all of our initial expectations for a raised bed material," Upson added. "It's worked for us, and it'll work for you."

For more detailed information on building multiple rubber board beds or other types of raised garden beds from tires, as well as directions on how to build less permanent beds from another less common source, plastic mesh, see Permanent Raised Bed Gardening: Vol. 1 - Novel Raised Bed Designs for Home and Market Gardens.