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Gardens that Last for Years - Raised Bed Gardens, 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:
1. 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.
2. 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.
3. 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.
4. 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.
5. 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
1. Level the garden plot.
2. Form a taut string line between two stakes.
3. 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.
4. 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.
5. 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.
6. Remove the sling and drive a 5/8th-inch rebar stake through the loop.
7. Align the opposite rubber board parallel to the first, the distance determined by the desired width of the bed.
8. Use two additional pieces of cut tread to form the end pieces.
9. 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, The Noble Foundation has published a 72-page color book, Permanent Raised Bed Gardening: Vol. 1 - Novel Raised Bed Designs for Home and Market Gardens.

To order the book or learn more about the Foundation's work, write Upson at The Noble Foundation, 2510 Sam Noble Parkway, P.O. Box 2180, Ardmore, OK 73402-2180, or call the Foundation at (580) 223-5810.

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Photos and cutlines for this article

More articles about raised bed gardening:
Permanent Raised Bed Gardening by Steve Upson
Fabricating Rubber Lumber (photo guide) by Steve Upson
Horticultural Information Index

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Note: Below is a short article on how to first plot out a site for a raised bed garden if the site is on sloped ground. If your magazine has not already run an article on plotting a sloped-site garden, you might like to consider this as a sidebar to the rubber lumber story, or as a stand-alone article to be run separately.

Plotting a Garden Site for Your Raised Bed Garden
Before construction of a raised bed garden can begin, plotting the site is crucial, according to Steve Upson, horticulturist with The Samuel Roberts Noble Foundation headquartered in Ardmore, Okla.

Although level sites are sometimes in short supply, they are best for raised beds, Upson said. However, sites that are uniformly sloped, and not too much so, are quite usable for raised bed gardens. Below are steps on how to best utilize and plot your garden site.

The Procedure: Plotting the Site
Plot the adequately prepared site with grade already established (level or uniform slope). This will require, in addition to the materials listed earlier, a carpenter's square, several small and large nails, twine or heavy string, eight wood stakes, measuring rod, a permanent marker, and two measuring tapes long enough to reach across the plot.

Mark one side of the plot, preferably parallel or perpendicular to a nearby building, road, fence line, etc. running east-west or north-south. If such is not available, use a compass to establish the first side. Drive two stakes (points A and B) several feet farther apart than the actual planned plot length. String a line between the two points. Press a large nail into the ground directly under the string at the plot's corner point (point C). Place a second nail at an adjacent corner (point D). Line CD represents one side of the plot.

Measure the distance to both corners on the opposite side (points E and F) and mark with nails. Use a framing square to make points C and D a 90-degree angle, then make sure corner C (points F, C, and D) forms a 90-degree angle, using the 3-4-5 triangle ratio.

A 90-degree angle is established at corner C by measuring a point 24 feet from point C and marking with a nail under the string. Attach two measuring tapes to the nails at points C and G. Place a nail at the union (point H) where the 32-foot and 40-foot marks of the tapes meet. Remove the tapes and attach a string between points C and F. Make sure the string is taut, but not enough to move the nails. If the string is not directly over point H, adjust point F accordingly. Corner C should now be a 90-degree angle. If the distance between points F and E are not the same as between points C and D, adjust point E. This should now make corner D 90 degrees.

If the lengths are unequal, follow these steps: 1. Adjust the location of only points E and F. 2. Move the nails in one direction along line EF, never towards or away from points C or D. 3. To make an adjustment, move the nails in the same direction and at equal distances.

Prepare eight 2-inch-by-4-inch-by-24-inch wood stakes. Drive a small nail into the broad, 4-inch side of each stake, 4 inches from the top. Place the stakes 18 inches from each corner, centering them on each boundary line. Drive the stakes into the ground a few inches (temporarily) with nails facing away from the plot. Select one stake and drive it to a height above the soil equivalent to the bed height (height of rubber board). Use a leveling instrument and leveling rod to establish remaining stakes at the same elevation (unless slope makes this impossible).

Establish the position of each boundary. Attach strings to the nails on each stake, placing strings over the tops of the stakes. Be sure each string is taut and use a carpenter's level or plumb bob to position strings directly above nail points. Mark the position of each string along the tops of the stakes with permanent marker or pencil.

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