Want happy streams, happy wildlife and happy people? Rain gardens with their display of colorful flowers, all geared to slow and capture water running through the yard, can be the answer.
Those eager to learn about installing a rain garden were educated by Chagrin River Watershed Partners Master Gardener Laura Bonnell during a recent webinar.
Mrs. Bonnell is a project manager for the Chagrin River Watershed Partners and teaches the Northeast Ohio Master Rain Gardener course. She was joined by Kevin Saracino, a member of AmeriCorps who is working with the watershed partners.
The virtual class on “friendly stream maintenance” was geared for communities, Mr. Saracino said. “Our main objective is education on the environment.”
So, what is a rain garden? “It’s a garden to receive storm water runoff,” Mrs. Bonnell said, noting that this water can come from roofs, sidewalks, driveways and other impervious surfaces where water does not infiltrate the ground. The water from the impervious surfaces is directed into the rain garden, which is designed and located to capture the stormwater. The garden helps put the water back into the ground before it makes storm sewers overflow, resulting in polluted streams and rivers, she said.
When the runoff water travels over the impervious surfaces, it can pick up and carry pollutants, yard debris, pesticides and chemical residues. Stormwater runoff can create severe erosion, flooding and it can damage nearby structures and habitats.
The Environmental Protection Agency has said such untreated run-off is a leading threat to our surface waters, Mrs. Bonnell noted.
Natural landscapes such as rain gardens can filter pollution and slow and cool the water, she said. The rain gardens in Northeast Ohio treat half-inch rain storm events. “If you have ponding or localized flooding in your yard, rain gardens help mitigate those issues,” she said.
If planted with native plants, the gardens can provide habitat for birds, bees and butterflies and provide attractive landscaping, Mrs. Bonnell said. “There are lots of benefits.”
In describing how to build a rain garden, she noted that a site near the water source should be chosen, and it can be in the sun or shade.
While the area chosen for a rain garden typically requires digging, they generally do not require a permit from the local community. A resident can check, but it is rare, Mrs. Bonnell said of required permits.
In selecting a site, make sure it is a minimum of 10 feet from the house foundation, she advised. The location, whether in sun, part sun or full shade, determines the types of plants to be installed. Placement should also be away from trees, septic fields, underground utilities and very steep slopes, according to Mrs. Bonnell.
The garden can be edged, but it should have an outlet for the excess water to escape to a safe place during heavy rain events, she noted. Planning the size of a garden can take into account different aspects, including the size of a roof or any impervious surface that is sending off water.
Determine the type of soil, such as whether it is well draining or poorly draining, she said. An average garden is about as big as a parking space, but can be larger or smaller.
Conveyance of overflow water to the garden basin can be by a pipe or swale, she said. A berm should hold the water in the basin to allow it to seep into the ground, and it should have an outlet for emergency overflow that directs excess water to a safe place.
“Keep the basin as flat as you can,” Mrs. Bonnell said. Depending on soil type, the rain garden will be from 3-6 inches deep, called the ponding depth. Below the ponding depth, amend 6 inches of soil with a mixture of a nutrient rich topsoil and compost, she said.
In planting, consider the rain garden’s location, Mrs. Bonnell noted. If it is in the front yard, some factors should be taken into consideration such as neighborhood esthetics. Make sure the shorter plants are in the front and the taller ones in the back for a better view. “Always consider the viewpoint,” she said.
Plan the color scheme, height, spread and bloom time. “It’s nice to have blooms throughout the seasons to always have color,” Mrs. Bonnell noted.
Native plants are preferred for the garden. Native plants have deep roots that improve soil infiltration, require less maintenance and provide wildlife habitat. “Native plants are the way to go,” she said.
Native shrubs and herbaceous perennials do well, and sun or shade tolerant plants could include blue flag iris, fox sedge and great blue lobelia. Good shade plants include wild ginger, ostrich fern and wild hyacinth. Plants tolerant of part shade include nodding wild onion, Canada anemone and red osier dogwood. The dogwood creates a winter interest plant, Mrs. Bonnell noted.
Other sun tolerant plants include switch grass, swamp rose mallow and New England Aster. Rain garden plant lists used by the Master Rain Gardener program are available on the Cuyahoga Soil and Water Conservation District website.
Spring and fall are the best times to plant. It is easier to dig in the spring, however, fall is the preferred time, when the perennials can put their energy into their roots, Mrs. Bonnell said. If done in the summer, the plants should be kept watered.
Water is necessary as part of maintenance to promote growth and survival in the first two years. The garden should be weeded, and clustering plants when planting makes it easier to weed the garden. Add or replace dead or dying plants, Mrs. Bonnell advised, and after planting, add 2-3 inches of hardwood double shredded mulch.
It is best to leave dead plants standing to help the bees, ladybugs, birds and predator insects, she noted. It provides a place for them over winter as well as a food source. The plants can be left through Mother’s Day and they provide winter garden beauty, she said.
In response to questions, Mrs. Bonnell said a rain garden is not a pond and should drain in 48 hours. It won’t attract mosquitos and does not need to be fertilized. The gardens can treat half-inch storm events, which is significant, she noted.