How to Plant a Rain Garden

There are a multitude of reasons why planting a rain garden would be beneficial for your yard and the environment. Read on to learn more.

What Is the Purpose of a Rain Garden?

Cost effective, eco-friendly, and aesthetically pleasing, rain gardens reduce runoff that would otherwise saturate your property, help eliminate contaminants from seeping into surrounding areas and also serve as healthy dwellings for butterflies and birds.

Rain gardens allow water to pool during a downpour, then slowly percolate into the soil. The shallow catch basin is a flower-bed destination for water rather than a travel route, like a swale. A fast-draining soil mix encourages water to sink in and promotes lush plant growth. Runoff may flow into a rain garden from a swale or pipe, or may simply run in from a sloping yard.

Rain gardens are appropriate drainage spots for steeper slopes than swales can handle, but where the surface drops more than 3 feet over a 15-foot horizontal distance, you should get professional design help. Although a low spot in the yard might seem an ideal placement, if it stays soggy, it’s already saturated. Instead, pick an area that dries out quickly.

Calculations and Design

Designing a rain garden to handle all the runoff from a roof or driveway entails careful calculations. But you can also learn by experimenting: Build one, watch what happens after a storm, and then enlarge it as needed.

Locate a rain garden at least 10 feet from your house and at least four times that far from a septic system or steep slope.

How Do You Build a Rain Garden?

Though you can excavate a small (say, 5-by-10-foot) rain garden yourself, a landscaper with an earth-moving machine will get it done faster. Make sure machinery stays along the edge of the bed so it doesn’t compact the soil as it digs a wide ­depression about 2 feet deep with gently sloping sides.

Mix in compost and sand, as needed, using the same proportions as for a swale. The result should be a shallow basin with about 6 inches of “ponding depth,” or space for water to pool while it drains through 1 to 2 feet of amended soil.

Steps:

1. Before digging, call the utility locating service to mark any underground pipes and wires.
2. Use marking paint to draw borders for the rain garden.
3. Scrape off any existing grass and roots in the garden location using a shovel.
4. Dig down 18″ using shovels and discard the removed soil. A pick axe may be used to break up heavier soil.
5. Add 1-2″ of coarse sand to the hole and spread it evenly with a metal rake.
6. Remove the plants from their nursery pots and stage in place.
7. Use a hand claw to tease the roots and encourage outward growth.
8. Backfill the hole using a soil mix that is 1/3 coarse sand, 1/3 compost, and 1/3 bark mulch.
9. Water the plants thoroughly, then cover in a layer of bark mulch.
10. Continue to water for a month until the plants are established and then the plants should survive on only rain water.

What Are the Best Plants for a Rain Garden?

Plant the center of the area with species that tolerate wet conditions, such as native sedges and lady fern. Around these, put plants suited to occasional standing water, like red twig dogwood. At the furthermost edges, add plants that prefer ­drier soil, such as native evergreen and deciduous shrubs.

What Materials Do You Need to Build a Rain Garden?

• Mulch
• Berm or stones
• Perennial plants
• Pointed shovel
• Pickaxe
• Wheelbarrow
• Metal rake
• Hand claw

Anatomy of a Rain Garden

A: Water flows in from slope, paved area, or pipe

B: Wide, shallow basin with flat, level bottom and gently sloped sides

C: 12 to 24 inches of fast-draining

D: 2 inches of mulch

E: 6 inches of ponding depth

F: Berm or stones to stem or slow down overflow

G: Perennial plants