How To Build A Rain Garden In Colorado To Capture Yard Runoff
A rain garden is a low, planted depression that collects runoff and allows water to soak naturally into the ground rather than immediately flowing off the property. Rain gardens can collect water from roofs, downspouts, lawns, driveways, and other surfaces. Rain gardens can be especially helpful for water management in Colorado’s climate by capturing precipitation and replacing portions of high-water-use turf with attractive vegetation. Rain gardens also attract beneficial wildlife, such as pollinating insects, and support overall water quality. Let’s discuss how to build a rain garden, including choosing the location, testing drainage, determining size and depth, and selecting plants for your Colorado rain garden.
What Is A Rain Garden And How Does It Manage Stormwater Runoff?
A rain garden is a strategically located shallow depression where runoff collects temporarily before infiltrating the soil. Water runoff from surrounding areas flows toward the garden, where the depression temporarily holds the water. Moisture-tolerant plants are placed around the depression, which helps hold the soil and slow water absorption. Rain gardens collect water and allow it to slowly enter the soil, rather than flowing down a storm drain.
A rain garden is not a pond and will not remain permanently filled with water. Ponds are enclosed containers designed to hold water, plants, and sometimes fish, while the purpose of a rain garden is to allow water to enter the surrounding soil slowly. Avoid placing rain gardens where water already pools, because that indicates slowly draining soil. Rain gardens can be naturally incorporated into landscaping, rather than looking like a drainage feature.
Where Should You Place A Rain Garden In A Colorado Yard?
Rain gardens in Colorado can be highly beneficial if placed properly:
Look for areas that naturally receive runoff from downspouts, roofs, lawns, driveways, and other impervious surfaces.
Always place rain gardens at least 10 feet from buildings and structures and 25 feet from septic systems.
Don’t place rain gardens close to established trees, where water naturally pools, or on steep slopes.
Be sure to identify and mark underground utilities, such as gas lines, before digging!
Consider where excess water will travel during especially heavy downpours; do not allow overflow toward neighboring properties, buildings, or the street.
According to Colorado State University (CSU), a good way to test drainage before starting to dig your rain garden is to dig a small 8-inch-by-8-inch test hole and fill it with water. If the water fully drains within 24 hours, it’s a good location. But if the water hasn’t drained, choose and test another location.
How Deep and Wide Should A Residential Rain Garden Be?
Determine the size of your rain garden based on how much drainage area you have, the soil type, infiltration rate, and how much runoff you’re capturing. According to CSU, the average rain garden is about 100–300 square feet. Another rule of thumb is to make the rain garden about 30% of the area draining into it.
Depth depends on your soil type. If you have clay soil, your rain garden should be no more than 6 inches deep, while sandier soils can be dug to 8–12 inches deep. Water moves more slowly through clay soil, so the soil needs to be shallower to accommodate the rate of water absorption. You can incorporate compost into clay soil to improve drainage.
When digging a rain garden, keep the bottom level and add a low berm (a small wall or barrier) on the downhill side to help contain runoff.
Which Native Colorado Plants Shine In A Rain Garden?
Your rain garden has three planting zones: the center zone, which is the wettest, the middle zone, and the outer ring, which is the driest. Since moisture levels in the rain garden will vary, all plants need to tolerate fluctuating moisture.
Good plants for the lowest, wettest zone include blue flag iris, common rush, sedges, and tufted hairgrass.
For the middle zone, where soil alternates between wet and dry, consider Rocky Mountain penstemon, blanket flower, blue grama, and prairie coneflower.
Options for the upper, driest zone include rabbitbrush, yarrow, little bluestem, and sulfur flower buckwheat.
A mix of grasses, flowering perennials, sedges, and rushes creates a fuller look while helping the garden handle both heavy rain and dry periods. Be sure to match native Colorado plants to sun exposure, mature size, and soil conditions before planting.
How Do You Maintain A Rain Garden Through Colorado's Seasons?
At the start of spring, remove accumulated debris from your rain garden. Check for any erosion from snowmelt and repair as needed. Cut back dead perennial growth as needed, and replace any plants that didn’t survive the winter.
During summer, water any new plants until they’re established. Now is the time to keep an eye out for weeds and remove them as needed. After summer storms, watch the rain garden to ensure water is infiltrating properly.
When fall comes around, check the inlet and overflow route for leaves and debris. Continue to remove weeds as needed. Leave appropriate native perennial material when beneficial for overwintering wildlife.
Wintertime care is fairly simple; allow established hardy perennials to go dormant naturally. Avoid compacting soil by repeatedly walking through the garden.
Other tips include adding 1-2 inches of mulch around newly planted plants, which reduces weeds and protects and enriches the soil. In general, newly planted rain gardens need more attention while plants establish, even when using Colorado natives.
Shop Native Rain Garden Plants At Bath Garden Center
Ready to build a rain garden in your Colorado yard? Bath Garden Center can help you choose plants suited to the different moisture conditions within your rain garden and the unique growing conditions here in Northern Colorado.
Before you visit, take note of your rain garden’s size, sun exposure, soil conditions, and where runoff will enter the garden. Our knowledgeable team can help you select native grasses, flowering perennials, and other plants that fit your space. You can also find soil amendments, mulch, and other gardening supplies to help establish your rain garden.
Visit Bath Garden Center in Fort Collins and let us help you turn yard runoff into a beautiful, functional addition to your landscape.
Resources:
Colorado State University Colorado Water Center. "Why plant rain gardens?" https://watercenter.colostate.edu/rain-garden-resources/
City of Fort Collins. "Recommended Native Plant List."
Colorado State University Extension. "How to Create a Rain Garden." https://landscapeforlife.colostate.edu/water/rain-gardens-and-bioswales/
