One of the best things you can do for your local environment is build a small rain garden. It’s amazing how a small, low-maintenance plot of garden can make such a difference. A rain garden absorbs large amounts of rainwater during storms, filtering it and putting it into the local water table and atmosphere rather than letting it flow unchecked into the water system to cause pollution and flooding downstream.
A well-designed rain garden can allow as much as 30 percent more water to soak into the ground as compared to a conventional lawn. If your rain garden is carefully placed in the path of downspouts (where a lawn is often difficult to keep healthy, anyway), this can mean a huge difference in how much water is filtered and absorbed into the local water supply.
The term “Rain Garden” refers to a low-lying area that collects water in heavy rains that has been planted with plants that thrive in such conditions. This can mean something as simple as choosing better-adapted plants to plant in low-lying areas of your landscape that already collect water, or it can be complicated enough to involve soil tests, landscape architects, and serious construction. Something in the middle is best for most gardeners. Any rain garden is better than no rain garden: every bit of runoff that you help to be filtered and reabsorbed helps to clean the water in your neighborhood, city, and anywhere downstream and keeps your local water supply healthy and plentiful.
The best rain gardens use a combination of four things to succeed:
- A low-lying area that collects water from the surrounding area and keeps it there long enough to effectively be absorbed
- Mulch to absorb and retain water, as well as to provide organic nutrients to the plants
- Plants that thrive in periods of flood and drought, absorbing and retaining large amounts of water in storm conditions
- Loose soil that allows water to be absorbed and transmitted into the water table.
Most gardeners have a pretty good idea what areas of their landscape already tend to collect water, and those are usually the best places to start your rain garden (though you can redirect rain to other spots). It’s especially good if water from your roof and lawn drain into this area. It is very important to build your rain garden at least ten feet from any building (also keep it away from large trees and septic tanks or drain fields).
To prepare your rain garden, dig the soil and loosen it to two feet deep to give the water room to infiltrate (as with any garden project, be aware of underground lines and utilities before digging). If the soil is clay-like or very dense, you may want to add looser soil to your garden area or even replace the clay entirely.
After loosening the soil you will now have have excess dirt. You can just move this to another part of your yard, or you can use it to build a low wall to block water in the rain garden area (this is called a “berm”). Slowing the water further will allow more water to be absorbed and filtered by your rain garden.
There are a variety of beautiful plants that are excellent for rain gardens. You’ll want to choose plants that are tolerant of both standing water and drought. Some of my favorites:
Hibiscus (Rose Mallow)
Whenever possible, use native plants in your rain garden. They are usually more adaptable to your climate.
The last important step is mulching. The right mulch will prevent erosion, keep the soil moist, and absorb some water itself. It will also replenish organics in the soil and discourage weeds, which helps to keep your rain garden as low-maintenance as possible. Mulch your rain garden heavily (two to three inches) with a heavy organic mulch. Coarse compost is best, as it will float less than wood chips or shreds. Do not use grass clippings, as they will overfertilize your soil.
Keep in mind that this information is for a small rain garden. If you’re planning a larger garden, you’ll want to do more research than what you find here. Check with your local university extension offices and gardening clubs to find out more: in most areas these groups will be more than happy to help you out. In many areas where watersheds are particularly threatened or where flooding is a problem, entire neighborhoods have pooled resources to build large rain gardens or many small versions, and this has made a huge difference in their areas.
When you have created your rain garden, please send us a quick email or FaceBook post to tell us how it’s working!