Here are two ways to grow flowers or vegetables in hard, rocky soil. The first is to dig out the top 12 in. of the old soil and replace it with a rich, fertile mix. But the better way is to build a raised planting bed. Here are its advantages:
- The raised bed is filled with a quality garden soil.
- The soil won’t become excessively compacted because you don’t walk on it. This allows for good drainage and air movement down in the root zone.
- The garden is easier to plant and maintain because it’s at a more convenient height. With the bed at 18 to 20 in. high, you can sit on the edge and work comfortably; 28 to 30 in. allows for wheelchair accessibility.
- If you’re working on a slope, the raised bed creates a level terrace.
- The planter becomes a strong landscape design element.
Make the raised bed planter as long as you wish, but limit its width to 4 ft. so you can work the garden from both sides. Reaching in more than 2 ft. is hard on the back. Consider the specific plants to determine the raised bed’s depth. It should be a minimum of 8 in. This will accommodate the roots of lettuce and radishes, but root vegetables and many perennials require more depth, so consider building it 12 to 18 in. deep.
While the raised bed can be built from any of a variety of materials, modular concrete retaining wall blocks ($4.50 each) are ideal. Their uniform shape makes them easy to install, they’ll last forever and their loose-laid installation allows for good drainage. Be sure to put a landscape fabric liner behind them to keep the soil from washing through the blocks.
A good general garden soil mix is one-third topsoil, one-third composted manure and one-third sand. First mix these together with a shovel and then fill the raised bed. Establish and maintain the soil’s fertility with mulch, com- posted organic material and/or chemical fertilizers.
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