An old boxspring mattress can make a wonderful planter box for herbs, certain vegetables and other plants that have relatively shallow roots. They are especially handy tools for gardeners with inadequate soil. Because these planter boxes rest on top of the ground, they can be filled with any soil of your choosing. However, not all boxsprings are equally suited for planting. Look for a box spring a complete wooden frame. Those with stiff fabric sides will mildew and rot when exposed to the elements.
Use a box cutter to cut away all of the fabric from the boxspring mattress. You should be left with a wooden box frame.
Carefully remove any interior springs with a pair of wire cutters, taking care not to damage the frame of the box spring. Do not remove any of the cross sections. They support the box spring. You will simply have to plant around them.
Paint the entire wooden frame with two coats of waterproof paint in the color of your choosing.
Put the box spring wherever you want your boxspring garden to grow.
Place a layer of lava rocks in the bottom to improve drainage.
Fill the planter with potting soil, and plant.