Ornamental grass will stop erosion from a rain garden's berm.
New Jersey averages between 25 and 30 thunderstorms every year. The heavy rains that occur during these thunderstorms run off of lawns and driveways and into public storm drains. As the rainwater passes over yards, it picks up contaminants such as pesticides, fertilizers and petrochemicals. These chemicals and rainwater travel from the storm drains to bodies of water all across the state of New Jersey, polluting the waterways. Rain gardens absorb some of the runoff into the soil. The earth is able to use and break down most of the chemicals, resulting in less contamination of New Jersey waterways. Does this Spark an idea?
Instructions
1. Determine a location at least 10 feet from a home's foundation. The site needs to have a slope between 1 and 10 percent and have good drainage. To determine drainage, dig an 8-inch hole with a garden shovel. Fill up the hole with water from a garden hose. Allow the water to absorb into the soil and refill the hole with water. Check on the water in the hole in three hours. If the water is gone, there is adequate drainage in the area. If not, you will need to find a different spot for the water garden.
2. Dig out the area for the rain garden, no smaller than 10 feet wide by 10 feet long by 1 foot deep, using a garden shovel. The larger the rain garden, the more rain runoff it can absorb. A garden 10 feet by 20 feet by 6 inches in size will absorb 90 percent of the rain New Jersey receives every year. Move all displaced soil from the rain garden area.
3. Move the displaced soil to the lower one-quarter of the rain garden. Build a berm, a mound of dirt, with the soil. The berm will filter and slow down the flow of the rainfall. Press down on the berm with the back of the garden shovel to compact the soil.
4. Pick up a handful of soil from the dug-out area. Squeeze the soil into the shape of a ball. Push your thumb into the soil ball. Soil that falls apart easily is sandy soil. Soil that depresses leaving the shape of your thumb behind is clay soil. The quality of the soil will determine how you add compost to the planting area.
5. Add a 3-inch layer of organic compost to the dug-out area of the rain garden. If your soil is sandy, use a garden rake to mix the compost into the top 3 inches of sandy soil. For clay soil, you must rototill the compost into the top 6 inches of soil.
6. Choose plants that are native to the New Jersey area for the rain garden. Good choices for plants in a New Jersey rain garden are cardinal flower - red, milkweed or Great Blue Lobelia. These plants are perennials that can grow to about 5 feet tall. If you want to add a shrub to the rain garden, both arrowwood and spicebush are flowering shrubs that will thrive in a rain garden.
7. Plant ornamental grasses on the berm. Ornamental grasses will stop the berm from eroding away from the rain runoff. Ornamental grass will not need to be mowed. Fountain grass and feather reed grass are good choices for berm plantings.
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