Rain Gardens

Rain . . . it's nature's way of nourishing our world and replenishing our water sources. However, many of our daily activities, from washing cars to fertilizing lawns, can turn this precious resource into an environmental problem. The flow of water created by a rainstorm - stormwater runoff - can be polluted by oil, chemicals, pesticides, and sediments built up on our lawns, driveways, streets, and parking lots, in this instance three acres of parking lot. Rain washes these pollutants into storm drains and ultimately into local streams and rivers. Look at our recently installed rain garden by clicking here.

The Problem with Storm Water:

The Environmental Protection Agency (EPA) has determined that up to 70% of the pollution in our surface waters comes from stormwater. We tend to think that most of this is caused by large industrial polluters, but this is not the case. Many studies have found that nearly 50% of that pollution comes from small businesses, individuals and homeowners, due to lawn care, household chemicals and automobile usage.

The Rain Garden Solution:

One way of reducing the non-point source pollution flowing into our streams and rivers is to install rain gardens on our property. A rain garden is an attractive native plant garden with a special purpose, to reduce and filter the stormwater entering our streams. It is constructed as a place to direct stormwater from roofs, driveways and parking lots, allowing water to be held in the plants, mulch and soil. Rain Gardens aren’t just for houses! In fact, the use of rain gardens for storm water management originated at commercial and industrial sites where space is limited, and
the installation and maintenance of conventional environmental practices, such as oil and water separators and stormwater ponds, is expensive.

Rain Gardens use the concept of bioretention, a water quality practice in which plants and soils remove pollutants from stormwater naturally. Rain Gardens are created in low-lying area, with specific layers of soil, sand, and organic mulch. These layers naturally filter the rain as it runs into the Rain Garden. During the next few days after a storm, the soil absorbs and stores the rainwater and nourishes the Garden's grasses, trees, and flowers. The traditional system of curbs, gutters, and storm drains carries stormwater runoff directly to local streams and rivers without any bioretention filtering process. Instead Rain Gardens filter and reuse the water, reducing stormwater pollution, while providing attractive landscaping.

In addition to their water quality benefits, Rain Gardens:

Promote your business’ environmental stewardship and community pride
Provide habitat for wildlife and native plants
Moderate air temperatures through evaporation
Increase real estate values by creating an aesthetically pleasing landscape

Components of a Rain Garden:

Mulch /Organic Layer
This medium provides for the decomposition of organic material. It also plays a very important role in the removal of metals. Shredded hardwood mulch is recommended because it allows for a greater surface area for binding and resists flotation/washout.

Planting Soil
Organic matter in the form of peat moss (10%) blended into a sandy soil (80%) with and about 10% top soil . This region provides a source of water and nutrients for the plants to sustain growth. Clay particles adsorb heavy metals, hydorcarbons and other pollutants.

Plant Selection
A planting plan design should include species that tolerate extremes. There will be periods of water inundation and very dry periods. Most riparian plant species will do well in rain gardens. The choice of species should include plants that mimic forest habitat and have an aesthetic landscape value such as flowers, berries, interesting leaves or bark. Groundcovers, perennials shrubs and trees should be incorporated into the planting design.

Site Considerations
Each site should be considered unique. Microclimates (light, temperature and wind), and the size of the drainage area will influence the size of the rain garden and plant selection process.

Frequently Asked Questions:

Question: Don't rain gardens attract a lot of mosquitoes?
Answer: No. For reproduction, mosquitoes require a number of days in standing water. Most urban mosquitoes breed in places like junk-piles where there are old tires or tin cans. There is rarely standing water long enough for mosquito reproduction in a well-designed rain garden.

Question: Can I create a rain garden that doesn't look too wild or messy?
Answer: The way to make a rain garden, or any garden, appear 'well kept' is to keep the edges tidy. Tall plants and grasses tend to "flop-over" so if you want a neat silhouette, you will want to stick with short species. To keep native plants from growing too large, remember not to water them!

Question: What happens to water-tolerant plants when we have a dry spell?
Answer: Native plants can withstand a range of weather conditions. Native plants that do well in poorly drained soil will be fine during dry weather.

Question: How large must a rain garden be to be worthwhile?
Answer: Any water that seeps into the ground instead of running into a storm sewer helps water quality. A rain garden of any size has a positive impact.

Question: How difficult are rain gardens to maintain?
Answer: Rain gardens are like any other garden. They require more care initially to establish the plan ts, but then only monthly inspections are needed to repair eroding areas, prune and repair vegetation and remove trash and debris.

Businesses That Install Raingardens:

Please note, this may not be complete. If you know of other businesses that install rain gardens in the Washingon, DC metropolitan area, please email their contact information to Steve Saari. This list does not constitute endorsement of these businesses by ARBC or any of its members.

Businesses That Have Raingardens: