Building a raised bed on a hillside takes a day or two, but the final result allows you and the kids to grow beautiful flowers, or vegetables and fruit, where previously there was only difficult-to-manage sloping ground. Raised beds improve drainage and provide favorable growing conditions for plants, especially if you add organic matter such as garden compost or well-rotted manure to the soil. Hillside raised beds should follow the contours of the hill. Adjust their depth according to the steepness of the slope.
So Many Choices
Walls around a raised bed hold soil in place and prevent heavy rains from washing it down the slope. Timber, stone, bricks and concrete blocks are all suitable for wall building. Regarding timber -- redwood and cedar hold up well to moisture. Use only untreated lumber to be on the safe side, since treated lumber may leach toxins into the soil. Like cedar and redwood, stone can be quite beautiful. If using stone, set it with mortar so it doesn't fall. Concrete blocks don't require mortar if the wall is 2 feet or shorter and you lay the blocks in a staggered pattern, but mortar will give additional strength, and it's needed for smaller construction materials, such as bricks.
Even inexperienced hardscapers can construct an effective 2-foot timber raised bed wall, providing the wall has foundations for stability and is strong enough to bear the weight of soil. Dig a trench half as deep as the width of the timber, and lay the timber pieces in a staggered pattern on top of one another. Drill holes through the wall and hammer rebar or metal spikes through to secure the timber wall and fix it in the ground. Don't let younger children near the drilling or hammering. Wear gloves when using tools and working with building materials. Alternatively, bury timber planks vertically, half in and half out of the soil, around the edge of the raised bed.
Step It Up
Terracing is another method for gardening on a hillside. Terracing calls for a set of raised beds. Each bed requires walls at the outer and inner edges for stability. After building the outer wall, move soil forward from the hill to create a flat surface in the raised bed. Then dig a trench at the back of the bed as deep as the height of the outer wall, and build the inner wall. Construct the outer wall of the second tier raised bed on top of the inner wall and secure the two together with metal spikes. Move soil forward to make a flat surface on the second tier, and continue in the same way up the hillside.
Walking and Watering
Hillside gardens are easier to maintain with access paths and irrigation. Installing irrigation lines saves time and effort watering plants. Simple stepping stones laid in flat trenches make walking up and down hillsides easier, but sloping paths are better for pushing wheelbarrows. Paths for wheelbarrows should also be at least 2- to 3- feet wide. Raised beds dry out faster than the surrounding soil, so lay drip irrigation lines across beds and attach to a water source to supplement rainfall, or grow drought-resistant, native plants in your raised beds.