Place the tractor tire where you want the raised bed to be. Consider the amount of sunlight needed for the plants you're going to grow.
Use a utility knife to carefully cut off the top sidewall of the tire. Removing the sidewall creates a larger growing space.
Shovel soil or a compost mixture into the tire until it reaches the top.
Plant seeds and water as needed.
Lay the tires on the ground in a single row where you want the retaining wall to be.
Fill the inside of the first row of tires completely with dirt, packing it tightly.
Add a second layer of tires on top of the first. Staggering them--placing them slightly behind and off-center from the first row--will give the wall more strength.
Fill in the new layer of tires with dirt.
Repeat steps 3 and 4 until the retaining wall has reached the desired height. Test the stability of the wall. It should not sway or rock when pressure is applied.
Plant a shrub, vine or other ground cover inside the top row of tires. The roots of the plant will add strength to the wall, and the foliage will help conceal it, giving it a more natural appearance.