Add a rain garden to your property
Have you ever watched the sheets of water flowing down your driveway during a rainstorm and wondered where it goes? That water goes into storm sewers, often carrying surface pollutants with it. Eventually the water ends up in lakes, streams and rivers. What if I told you that you could keep more of that water on your property and filter it at the same time? It’s easier than you think!
What is a rain garden?
All you need is a rain garden, a shallow, plant-filled depression that catches and holds water. As the water percolates through the root-filled soil, pollutants are filtered out. And the rain soaks deep into the ground, helping replenish local under- ground water supplies.
Tips from a pro
Plus, a rain garden will attract birds, butterflies and lots of compliments, too. To figure out how to make a rain garden, I spoke with Lisa Reas. As the owner of LJ Reas Environmental Consulting Corporation in Green Lake, Wisconsin, she has designed and installed many rain gardens. She shared these helpful tips.
Considerations for designing a rain garden
Start by looking at the water draining from your house through your downspouts. In the best case scenario, the size of the rain garden should match the size of the roof area that feeds into it. As an example, the house in the illustration below has a footprint of about 1800 square feet. We estimate that a sixth of the roof, or 300 square feet, drains to the downspout just off the driveway.
To handle the runoff, the rain garden in the foreground of the illustration ideally should be 300 square feet, too. You could make one big rain garden if you could direct several downspouts into it. However it’s often easier to build a separate one near each downspout. That way you won’t have to run long extensions to carry the water. So, to handle water from another part of this roof there’s a second rain garden near the back of the house in the upper right hand corner of the illustration.
Rain gardens can be any size you wish.
Bottom line: Any size rain garden is better than none. Even if they can’t hold all of the water, the excess will flow out onto the lawn. Just make sure it won’t flow onto a neighbor’s property.
Choosing the best spot for your rain garden
To keep water from seeping into your basement, rain gardens should be at least 10 feet downslope from your foundation. The house above has underground tile to route the water directly into the front garden, and a dry stream bed sends water to the back garden. Downspout extensions would also work for this. Don’t put a rain garden over a septic field; all of the excess water could overwhelm the drainage system. And if you already have a spot where water collects, that’s not a good location. Water puddling is usually an indication of poor drainage.
Beware of mosquitos
You don’t want your garden to breed mosquitoes, either. They need seven to 12 days to lay and hatch eggs, so make sure your water drains within 24 hours and you’ll be fine. Before you install, find out if your soil drains quickly enough: Dig a hole 6 to 8 inches deep and fill it with water. If the water doesn’t drain away in a day, try another spot.
Rain gardens are easy-care once established
Depending on how much rain you receive, you may need to do some extra watering the first two years to get the garden established. When you water, soak the soil deeply to encourage plant roots to grow down into the soil. Now that you have the basics, it’s time to dig the basin.
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How to dig a rain garden basin
The average rain garden should be set in a 6- to 8-in. basin with a level bottom, so water flows evenly into all parts of it. However, if you plan to add mulch, dig the garden about 2 in. deeper.
Stake out the area for your rain garden
After you test for drainage, locate your utilities and have the best location, you want to stake out the area. As you see in the illustration above, you’ll need at least two stakes.
- Drive one stake into the ground at the highest point where you’re putting your rain garden.
- Place a second stake down-slope.
- Tie a string as low as you can on the upper stake.
- Attach a string level on it (you can pick one up at your local hardware store) and stretch the string to the lower stake.
- Adjust the string until it’s level and then tie it to the stake. This is your guide as you dig.
Start digging your rain garden basin
You want the bottom to be level, so starting at the lowest stake, remove just a thin layer of soil. As you continue digging toward the upper stake, dig deeper and toss the soil just outside the lowest stake to build a berm.
Make sure the bottom of the basin is level
As you dig, frequently check the distance from the string to the bottom of the basin to make sure the bottom is level. For a large garden, pound in extra stakes around the low side and run strings to the highest stake so you have more spots where you can check the level.
Add plants to your rain garden
To give your plants the best start, till the basin and rake it level before planting. Then gently slope the edges so they won’t collapse when the soil’s saturated. After you finish planting, spread 2 in. of mulch to keep the garden moist between rains, free of weeds and looking good.
