Choose one tire to be the tower base.
Using a tape measure and a white marker, make six evenly spaced lines on the tire as shown.
Cut the top chain-link rail fence tubing into six, 60-inch long posts. Remove burs on the tubing.
Drill a 5/16-inch bolt hole, 10 inches from one end, in each post.
Install posts using 1-inch pipe straps and 1-inch self-tapping sheet metal screws. Use two straps per post. Before attaching post to tire, place a short piece of two-by-four lumber under the post.
Align the center of each post over the mark, and use a level to ensure the posts are plumb before attaching.
Insert bolts into holes at the end of each post, and secure using nuts. Make sure bolts on opposite posts are aligned with each other twisting posts as needed to align.
When posts are aligned, attach hangers to posts using ¾-inch tek screws.
Create three planter modules by removing the side walls from the remaining tires. On one side of each tire, use a utility knife to remove the side wall as close to the tread as possible without exposing the steel belting. A jigsaw equipped with a fine-toothed hacksaw blade or rubber cutting blade can also be used for side wall removal. Save one of the side walls.
To prepare the opposite side of each tire (planter module), mark the side wall along the midpoint (crown). Cut along the line to remove the side wall. This section of side wall may be discarded.
Construct a bottom for each module using a piece of plastic lattice or metal livestock panel. Using the saved sidewall as a template, mark off three bottom sections using a permanent marker. Use a jigsaw to cut the lattice or a pair of bolt cutters to cut the metal panel.
Prepare a liner for each bottom using a piece of weed barrier fabric. Use binder clips to attach fabric to the outer edge of the bottom sections or gather the fabric on the back side and secure using Gorilla tape.
Insert one of the growing modules into the tower frame and position on top of the base.
Next, insert the fabric bottom.
Attach the planter module to the frame using pipe hangers and sheet metal screws. One pipe hanger per post is sufficient. To avoid injury, grind off protruding screw tips.
Move tower to a permanent, level location before adding growing medium.
Use soil mixes high in organic material, such as peat moss and composted pine bark, to reduce weight on the tower frame.
Steve Upson serves as a senior soils and crops consultant with horticulture as his expertise area. Upson specializes in raised bed and container gardening, vegetable plasticulture, and hoop house vegetable and small fruit production. He also provides consulting services to organizations interested in starting community and school gardens. Prior to joining the Noble Research Institute in 1988, Upson managed a commercial vegetable farm and served as an extension horticulture agent for Oklahoma State University.