Originally Posted in Gunpowder Valley Conservancy Newsletter: Fall 2012
Want to make a positive impact on your local stream and the Gunpowder River Watershed? Interested in creating fall and winter beauty in your garden? Then we have a great fall planting project that will delight your eyes with color during the bleakest winter days and entice cheery winter songbirds to stop by for a visit and a snack! A rain garden is a slightly sunken garden designed specifically to collect and filter rainwater. They are designed to temporarily collect storm water runoff from impervious surfaces such as roofs, driveways, walkways and patios or even lawn areas. They allow this excess water to slowly percolate into the soil, which is then absorbed by plant roots, acting like nature’s sponge. This provides benefits including flood control, groundwater recharge and erosion control. Additionally, the soil and plants can absorb pollutants such as pesticides, oils, and metals.
The best site for a rain garden is in the drainage path of water flowing from impervious surfaces or in the path of downspout drainage from the house or garage. For this planting design, the garden should be sited in a spot that gets at least 6 to 8 hours of direct sun. Be sure to have all underground utilities located prior to digging! To start, lay out the shape of the rain garden bed and excavate to create a basin shaped ‘pond’ area approximately 18 inches deep. Some of the soil generated from this excavation process can be used to create a ‘berm’ on the lowest side of the rain garden to hold water in the basin area. Refill the basin you created with a blended soil composed of 50% clean sand, 25% compost and 25% topsoil. The finished elevation of the soil should be 3 to 6 inches below the existing, surrounding grade. This will allow the rain garden to capture and hold more run off water, especially during very heavy rainfalls.
Rain gardens are great habitats for songbirds, butterflies and beneficial insects. Don’t worry about mosquitoes because, while water may pool during and shortly after a rainfall event, it will dissipate long before the 7 days period mosquitoes need to hatch. It’s a great way to add beauty and provide environmental benefits in your own back (or front) yard. Just remember: rain falling in your yard will eventually make its way to the Chesapeake Bay!
Fall is such a great time of year for planting. Cooler temperatures stimulate root growth and the plants chosen for this example design will provide tremendous beauty and color during fall and winter months. These plants will grow well in both wet and dry conditions, handling the fluctuations in natural rainfall with ease. Here’s a look at the native plants and cultivar of native plants selected for this rain garden:
Shrubs:
Red Twig Dogwood
Cornus Sericea ‘Farrow’ Artic Fire
This winter beauty will mature at 3-4 feet in height. It is a compact shrub that will have reddish/purple fall color and dark red stems through the winter. Periodic renewal of this shrub by cutting back older stems to the ground will allow the brighter red color of the younger stems to show.
Winterberry
Ilex Verticillata
These deciduous hollies loose their leaves in the fall, but have brightly colored berries that last through the winter months. Three different cultivars have been selected to maximize color impact. ‘Winter Red’ has brilliant red berries and ‘Winter Gold’ has yellow/orange berries. The mature height is 6-8 feet. Both will attract fruit eating birds (such as Cedar Waxwings, Bluebirds and Mocking birds) in late winter. You will also need the male pollinator plant ‘Southern Gentleman’ to produce the berries.
Ornamental Grasses:
Tufted Hair Grass
Deschampsia cespitosa
This native grass, with its dense shiny green blades, is a perfect contrast to the broader leaves of the shrubs. The flower heads are much lighter in color, creating a haze of buff tones that stand out boldly against darker, evergreen foliage. From 2 to 3 feet in height, the foliage should be cut back in early spring before new growth flushes in.
Red Switch Grass
Panicum virgatum ‘Ruby Ribbons’
Summer foliage is metallic blue with red overtones. Airy, red seed heads form in mid to late summer. As the cooler temperatures of fall arrive, the foliage turns deep burgundy red. The plant will grow to about 4 foot in height. Leave the dried foliage for structure in the winter garden and cut it back in early spring.
Flowering Perennials:
Smooth Aster
Aster Laevis ‘Bluebird’
Growing 2-3 feet in height, this native cultivar blooms a profusion of deep lavender to violet flowers in September to October. Expect lots of butterfly visitors, especially migrating Monarchs!
Pink New York Aster
Aster novae-belgii ‘Woods Pink’
This one will offer clear pink daisy like flowers with a gold center. Bloom time is August to October and they grow about 12 inches tall.
Turtle Head
Chelone glabra
This native perennial has unusual snapdragon like white flowers in August to September. It’s an important food source plant for the caterpillar of
the Baltimore Checkerspot Butterfly, Maryland’s State Insect!
Dwarf Goldenrod
Solidago ‘Little Lemon’
Fluffy yellow flowers bloom in late summer through the fall, at 12 to 16 inches in height.
Highlight on the Author:
In addition to serving as a board member for the GVC, Kirsten Coffen, ASLA, is the owner of Garden Architecture, LLC, a landscape architecture firm located in Fork, Maryland. With a focus on environmental sustainability, the firm offers expertise in the design of rain gardens and bioretention facilities, native and wildlife habitat plantings, rain permeable hardscapes, ‘green’ retaining walls and water harvesting solutions. For additional information about Garden Architecture, LLC, please contact us.