A rain garden is a landscaped area that is designed to collect and absorb stormwater runoff from impervious surfaces such as roofs, driveways, patios, and sidewalks. Rain gardens help reduce flooding and erosion, improve water quality by filtering out pollutants, replenish groundwater supplies, and provide habitat for birds, butterflies, and beneficial insects. With some planning and labor, you can build an attractive rain garden in your yard that will benefit the environment and beautify your landscape.

What Are the Benefits of a Rain Garden?

Installing a rain garden on your property provides many advantages:

Reduces Flooding and Erosion: By collecting stormwater and allowing it to infiltrate into the ground, a rain garden decreases the amount of water that runs off your property. This alleviates pressure on storm drains and helps prevent downstream flooding and erosion.
Filters Pollutants: As stormwater flows through a rain garden, it gets filtered by soil, microbes, and plants. This removes contaminants like fertilizers, pesticides, motor oil, and road salts that would otherwise pollute streams and rivers.
Replenishes Groundwater: The water absorbed by a rain garden seeps down into the water table rather than running off the surface. This recharges local groundwater supplies.
Attracts Wildlife: The native plants used in rain gardens provide food and habitat for birds, butterflies, bees, and other beneficial wildlife.
Enhances Aesthetics: Rain gardens can be landscaped with colorful flowers, grasses, shrubs, and stones to create an attractive feature in your yard.
Low Maintenance: Once established, rain gardens require little weeding, watering, or mowing compared to a conventional lawn.

How Does a Rain Garden Work?

Rain gardens are bowl-shaped landscape beds that are situated near a runoff source like a roof downspout. They are dug out and filled with a layer of gravel, topsoil, mulch, and native vegetation that can tolerate both wet and dry conditions. The components of a rain garden work together as follows:

Stormwater flows into the shallow, concave rain garden bed via a swale or downspout.
The mulch layer helps spread and slow down the water flow as it enters.
Water filters through the vegetation and top layers of soil which trap pollutants.
Below the soil is a gravel layer that allows excess water to quickly infiltrate into the ground.
Native plants adapted to moisture fluctuations help absorb and transpire stormwater.
Any overflow drains out an outlet or spillway at the downstream edge.

This enables the rain garden to absorb rainwater runoff from up to a 1-inch storm. By diverting water into the garden bed, less runoff enters the storm drains, resulting in reduced flooding and higher water quality in nearby streams.

Where Should You Locate a Rain Garden?

When deciding on placement, here are some factors to consider:

Proximity to Runoff Source: Position your rain garden downhill from a runoff source like a roof, driveway, or compacted lawn area. Use drainage swales to direct water into the garden.
Soil Percolation: Test your soil’s drainage rate by digging a hole 12 inches deep and filling it with water. If the water doesn’t drain within 24 hours, you may need to amend the soil or locate your garden elsewhere. Well-draining soil is crucial.
Slope and Elevation: Choose a relatively flat spot for your rain garden, avoiding steep slopes. Pick an elevation below runoff sources so gravity moves water into the garden.
Sun Exposure: Most native rain garden plants need at least 6 hours of sun daily. Consider sun patterns when choosing the garden orientation.
Utilities: Call 811 before digging to locate any buried utilities. Ensure the rain garden is at least 10 feet from a house foundation or septic system.
Size: Ideally a rain garden is 5-20% of the size of its drainage area. Gauge your landscape to accommodate the required footprint.

How Big Should a Rain Garden Be?

The surface area and depth you need for an effective rain garden depends on:

The drainage area or amount of impervious surface runoff flowing into it.
The infiltration capacity of the soil.
How much runoff you want to control.

To size your rain garden:

Calculate the drainage area in square feet – this includes the house roof, driveway, patio, walkways that will drain into the garden.
Determine your soil’s infiltration rate through a percolation test. Sandy soils may infiltrate 8-12 inches per hour while clay soils infiltrate 0.25 – 1 inch per hour.
Use an online rain garden sizing calculator to input your square footage and soil type and get the recommended rain garden size and depth to capture 1 inch of stormwater runoff.
If you want to capture more runoff or have a larger drainage area, make your rain garden bigger or deeper than the minimum recommended size.

For most residential rain gardens, a size of 100-300 square feet and 4-8 inches deep works well. Position your rain garden where it can overflow into your lawn if it exceeds capacity during heavy rain.

How to Build a Rain Garden in Your Yard

Constructing a properly functioning rain garden takes some planning and labor but is completely feasible for a motivated do-it-yourselfer. Follow these steps:

Choose a Site and Size

Evaluate your yard layout and select an appropriate low-lying site where the garden can intercept runoff flow.
Determine the drainage area size and test the infiltration rate through a percolation test.
Use a rain garden sizing calculator to get the recommended dimensions to absorb 1 inch of stormwater.

Test Your Soil

Take several soil samples from around where you plan to dig the rain garden to a depth of 12 inches.
Send the samples to your local extension service for analysis to determine the soil texture and organic content.
Or do a percolation test by digging a 12-inch hole, filling it with water, and timing how long it takes to drain completely.

Design and Mark the Shape

Decide on a rain garden shape that fits your landscape. Kidney bean and teardrop designs work well.
Mark the outline with a garden hose or string and stakes. Adjust to fit your space as needed.
The length-to-width ratio should be at least 2:1 for proper water distribution.

Dig the Garden Bed

Remove grass/sod within the marked area using a sod cutter or shovel.
Excavate the bed to the recommended depth based on your drainage area and soil type, creating a bowl shape.
Slope the sides gently at about 45 degrees – make the slope less steep if kids or pets will access the garden.
Use excavated soil to create a berm on the downhill edge to help retain water in heavy rain.

Improve the Soil

Till 2-3 inches of compost into the native soil to improve organic matter and permeability.
For sandy soils, mix in topsoil or compost to help retain moisture.
For clay soils, add organic matter and consider incorporating sand or pea gravel.

Add Underground Drainage

Line the bottom with 2-4 inches of pea gravel or river rock.
Install perforated PVC pipe along the bottom if you want to connect to an underground drainage system.

Direct Downspouts/Runoff In

Use a drainage channel or swale lined with river rock to direct downspout water and runoff into the rain garden.
Add a stone splash block where runoff will enter to prevent erosion.

Plant Native Vegetation

Select a variety of native perennials, grasses, shrubs, and trees that can tolerate both wet and dry periods.
Group plants with similar water needs within the garden.
Plant the deeper center more densely and the slopes more sparsely.

Add Mulch and Finishing Touches

Put down 2-3 inches of shredded hardwood mulch across the whole rain garden bed.
Add aesthetic features like stepping stones, ornamental rocks, or benches around the rain garden.
Install a sign to identify your rain garden and educate others about its benefits.

Caring for an Established Rain Garden

Once planted, a rain garden requires some periodic maintenance:

Watering: Water plants during the first year while roots establish. Ongoing watering is usually unnecessary except during droughts.
Weeding: Expect more weeds initially – remove by hand or add more mulch to suppress them. Weed less as native plants fill in.
Pruning and Thinning: Cut back dead vegetation in spring. Thin overgrown plants to retain proper coverage.
Re-Mulching: Replenish the mulch layer annually or as needed to suppress weeds.
Overflow Pruning: Trim back vegetation blocking overflow outlets. Remove built-up sediment.
Plant Replacement: Replace dead plants, especially when establishing the rain garden. Refill mulch in holes.
Mosquito Prevention: Improve drainage and prune dense foliage to reduce mosquito habitat. Add mosquito dunks if needed.
Aesthetic Upkeep: Maintain the garden appearance by tidying up debris, refreshing mulch, removing invasive weeds, and pruning overgrowth.

Ideal Native Plants for Rain Gardens

These types of plants thrive in rain gardens in most regions:

Flowers: Bee balm, black-eyed susans, blazing stars, blue flag irises, cardinal flowers, great blue lobelia, wild bergamot, wild columbine, wild geranium, wild lupine.

Ferns: Cinnamon fern, royal fern, sensitive fern.

Grasses: Big bluestem, little bluestem, switchgrass, tufted hairgrass, Virginia wild rye.

Sedges: Tussock sedge, fox sedge, yellow sedge.

Rushes: Path rush, torrey rush, spike rush.

Shrubs and Trees: Buttonbush, elderberry, ninebark, red twig dogwood, serviceberry, swamp rose, winterberry.

Consult local resources to choose native plants suitable for your specific USDA hardiness zone. Mix sun-loving and shade-tolerant varieties.

Rain Garden Design Tips and Ideas

Incorporate flagstones, gravel pathways, large boulders, and log edging to add landscape interest.
Select a mix of heights, shapes, and colors for visual appeal through spring, summer, and fall.
Plant densely during rain garden establishment to help condition the soil and prevent weed growth.
Edge the garden with upright plants like grass or sedge to keep mulch contained.
Add a rain chain or decorative downspout to divert roof water into the basin.
Install a small ponding area lined with river rock at the inlet to settle sediment before it enters the garden bed.
Avoid invasive species like purple loosestrife which may spread aggressively. Utilize native plants instead.
Group plants with similar needs – bog species near inlet, drought tolerant near outlet.
Include plants that provide food and habitat for birds, bees, and butterflies to help local wildlife.

Common Rain Garden Issues and How to Solve Them

Standing Water: Improve drainage by adding a gravel sump, spraying soil amendments, or replacing clogged soil. Or plant more water-tolerant species.

Erosion: Stabilize inlets with splash blocks and line swales with river rock. Cover bare spots with erosion control mesh until plants establish.

Vegetation Dies: Use hardier plants, improve soil quality, provide more or less water depending on plant needs, and replant dead areas.

Weeds Take Over: Keep weeds in check by hand pulling, applying mulch, and ensuring dense plant coverage. Avoid using fertilizers or chemicals.

Too Dry: Improve water retention by adding organic matter, replacing gravel layer with leaf compost, or installing irrigation in drought-prone regions.

Mosquitoes: Prevent stagnant water by improving drainage, aerating soil, and eliminating low spots. Introduce mosquito predators like dragonflies.

Mulch Floats Away: Use shredded hardwood mulch and create an edge with rocks or plastic lining to keep mulch contained.

Animals Burrow In: Install wire mesh fencing below mulch to prevent tunneling. Make gentle slopes to deter rodents. Avoid dense vegetation that offers hiding spots.

Looks Messy: Tidy up the rain garden appearance in fall and spring by removing debris, pruning dead growth, refreshing mulch, and thinning plants.

Frequently Asked Questions About Rain Gardens

What is a rain garden?

A rain garden is a shallow, dug-out landscape bed planted with grasses, wildflowers, shrubs, and other native vegetation that can tolerate both wet and dry conditions. Rain gardens are designed to absorb and filter stormwater runoff from surrounding hard surfaces.

Where should I put a rain garden?

Install your rain garden near a runoff source like a roof downspout. Choose a relatively flat spot that is downhill from the runoff source with full or partial sun exposure and well-draining soils.

What size does a rain garden need to be?

Rain garden sizing depends on your soil type, the drainage area size, and how much runoff you want to capture. Use an online rain garden calculator for recommended dimensions, but make it bigger if you have a large drainage area.

How much does it cost to build a rain garden?

A basic 100 sq. ft. residential rain garden can be built for $3-$10 per square foot, or $300-$1000 total depending on soil improvements needed. Larger or more complex rain gardens cost $15-$40+ per sq. ft. installed.

What kind of soil do you put in a rain garden?

A mix of 50-60% sand, 20-30% topsoil, and 20-30% compost creates an ideal rain garden soil blend. For clay soils, add compost and sand. For sandy soils, add topsoil and compost to retain moisture.

What plants are best for rain gardens?

Choose native perennials, grasses, shrubs and trees that can tolerate both wet soil and dry periods. Good options include flowering plants like blazing star, iris, milkweed, asters, and bee balm mixed with grasses, sedges, rushes, and woody shrubs.

How often do you water a rain garden?

Once plants are established, rain gardens typically don’t need supplemental watering except during unusually dry periods. Water every other day for the first two months while plants develop roots, then wean off irrigation.

Do rain gardens attract mosquitoes?

Rain gardens don’t increase mosquito breeding if designed properly with good drainage. Ensure the garden drains fully within 24-48 hours to prevent standing water where mosquitoes can breed.

How can I make a rain garden look attractive?

Add aesthetic features like winding pathways, ornamental stones, log borders, bee houses, and plant labels. Select a variety of plants with different heights, colors, bloom times, and textures for visual appeal.

Conclusion

Installing a rain garden provides many environmental and aesthetic benefits. By following the guidelines here on site selection, sizing, soil preparation, plant choices, and construction, you can create a beautiful rain garden matched to your yard’s drainage pattern and landscape style. Maintain your rain garden by weeding, pruning, and replacing vegetation as needed to keep it functioning properly for years to come. With some planning and labor, you can build a rain garden yourself and make a positive impact on local water quality and wildlife habitat.

What Is a Rain Garden? How to Build One in Your Yard

Introduction

A rain garden is a shallow, vegetated basin that collects and absorbs stormwater runoff from rooftops, driveways, patios, and other impervious surfaces. Rain gardens are a beautiful way to reduce flooding and improve water quality in your neighborhood. By channeling runoff into the garden, rain water is slowed down, filtered by plants and soil, allowed to soak back into the ground, and used by vegetation. With some planning and digging, you can create a rain garden in your yard that will capture rainwater, help replenish groundwater supplies, and provide habitat for birds, butterflies and beneficial insects. This guide provides information on how a rain garden works, how to size and build one, tips for choosing the right location, what vegetation to plant, and how to maintain your rain garden so it stays healthy and attractive. Installing a rain garden is a rewarding way to manage stormwater responsibly while adding color and interest to your landscape.

How Does a Rain Garden Work?

A rain garden is positioned near a runoff source like a roof, driveway or impermeable lawn area. It is dug out to create a shallow basin shaped like a bowl or saucer that collects and temporarily stores stormwater runoff during rains. The layers inside a rain garden mimic the structure of a natural forest floor:

Ponding Area: Stores runoff temporarily after rain events before it filters into the ground.
Mulch Layer: Protects soil from eroding and keeps it moist while providing habitat for microbes.
Planting Soil & Vegetation: Native flood-tolerant plants help absorb water through their roots while soil and microbes filter out pollutants.
Drain Rock Layer: Gravel under the soil allows excess water to quickly infiltrate into the ground below.
Uncompacted Soil: Allows stormwater to percolate down through loosely packed soil into the water table.

The components of a rain garden work together to capture, absorb, and clean stormwater runoff. By diverting water into a rain garden, less runoff ends up in storm drains or gets chan