| Are you looking to make better use of the water on your property, or have a natural low spot that you don’t know what to do with? Installing a rain garden might be the answer for you! Rain gardens are gardens made up of native plants in a small depression in the ground that collects water flowing downhill. They make use of the rainwater that your property naturally receives, as well as filtering that water and allowing it to infiltrate into the ground instead of running off and carrying excess nutrients and silt into our waterways. We’ll go over the process of installing rain gardens to see if they’re right for your landscape. |
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| The first thing that you’ll need to do is measure and calculate the drainage area that you plan to collect water from, which is an impervious surface like your roof, driveway, or sidewalk. You’ll then need to pick a site for the garden itself. It should be at least 10 feet away and downhill from any buildings, and it must be feasible to direct water to an inlet (and outlet) for the garden. |
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| A soil percolation test is next, which will give you how deep the basin of your rain garden needs to be. To do this, dig a 1 foot deep x 8 inch wide hole, fill it with water, and measure how long it takes the water to infiltrate the soil. If it drains 6 inches in 12 to 24 hours, your basin should be 6 inches deep. If it drains 4 inches in that time, then it should be 4 inches deep. Most rain garden basins are 4-6 inches deep, and never more than 8 inches deep. Next, you’ll determine the size of your rain garden. You’re aiming for 20-30% of the drainage area (the impervious surface that you’ll be directing water from) to manage runoff from a 1 inch rainstorm. You just multiply your surface area by the percolation rate to find the area of your rain garden. Calculations: ● 6 inch rate – Multiply the area by ⅙ (rounded from .17 to .20)… so if your surface area was 1,000 square feet, your equation would be: 1,000 square feet x .20 = 200 square feet ● 4 inch rate – Multiply the area by ¼ (.25 rounded to .30)… so if your surface area was 1,000 square feet, your equation would be: 1,000 square feet x .30 = 300 square feet. |
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| The next step is drawing up your plan. You’ll want to plan drainage inlet and outlet routes for water to travel into and out of your garden, and the garden should have a flat basin, tapered sides, and a berm or mound which will prevent erosion on the “low” side of the slope. Your inlet and outlet should be protected from erosion with cobble or stone. The outlet must be lower than any nearby window wells, and below the bottom of the inlet pipe to make sure that water is going the right direction. When planning your plants, keep moisture loving plants at the bottom of the basin, with plants more tolerant of drought on the sides and top edge. We often refer to the plants’ Wetland Indicator Status, which you can learn more about HERE: When you’re ready to dig, make sure you call OUPS (Ohio 811) before you put shovels to soil so that they can mark any utilities. Outline and edge your garden, and remove sod which you can reuse elsewhere, especially in the mound on the downhill side of the garden. Make sure your basin is flat, and dig 6 inches LOWER than your planned finished depth since you will add topsoil and 2” inches of compost back into the garden. Lastly, wait until the garden is fully prepared to hook up the drainage pipes into and out of the basin. Calculations: ● For compost coverage – take the surface area of your garden and multiply it by 2/12 to get the cubic feet of compost needed for 2 inch coverage. X square feet x 2/12 = cubic feet of compost ● To convert cubic feet into cubic yards: X cubic feet / 27 = cubic yards |
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| Before planting, observe the garden’s performance after it gets some rain. If you have a long delay between preparing the site and planting, go ahead and mulch the rain garden to suppress weeds. When planting, avoid compacting the soil by standing on wide boards. After planting, top dress with the final layer of non-floating mulch (around 2 inches), water heavily to saturate the soil, and you’re good to go! From there, just care for it as you would any other garden. Water it 1-2 times per week until it’s established (or a hard freeze). One difference though is that you’ll want to keep the inlet and outlet clear of debris, including removing leaves to prevent fine sediment build up which would clog the rain garden. |
January 2025 Newsletter
