This is a fascinating article about a rain garden that was built in a space between two buildings in New York City. I thought is was so interesting and applicable to so many non-garden locations that I borrowed what was pertinent from
The New York Times (they’ve got so many articles, I’m sure they won’t mind just this one).
Building A Rain Garden
Ever wonder what happens to a rain garden when temperatures outside creep toward 100 degrees and it hasn’t rained in weeks
Water-loving plants wilt, of course. Especially if they are growing in just eight inches of soil, next to a dry bed of river rocks in a concrete courtyard at Teachers College of Columbia University.
“They don’t look fantastic, that’s for sure,” said Marni Majorelle, 31, the founder of Alive Structures, the Brooklyn garden design firm that created this garden and specializes in turning patches of concrete into natural (or seemingly natural) habitats. “We do have to water during times like this.”
But that water doesn’t tap the city’s supply; it runs from a 300-gallon rain barrel that collects water off the roof. Ms. Majorelle’s husband, Eric Majorelle, 29, who manages construction of the firm’s projects, set up the barrel and designed a catchment system for the downspout that pours into the rain garden.
The 400-square-foot garden, a narrow, undulating form that stretches 80 feet across an old interior courtyard tucked behind university buildings on 120th Street and Amsterdam Avenue, is filled with plants you might see growing along the banks of a forest stream. Juncus (also known as rush) and equisetum (or horsetail), ancient plants that love to have their feet in water. Ferns and swamp azalea, a fragrant native with white clovelike flowers that attract hummingbirds and butterflies. Northern blue flag irises, blue-eyed grass and, here and there, small shrubs of mountain laurel, a woodland plant that thrives in damp soil, but needs good drainage.
“I elevated the mountain laurels, with lots of gravelly mix around the root balls, so they wouldn’t sit in water,” Ms. Majorelle said.
By Mr. Schumacher’s calculations, about 30,000 gallons of rainwater pass through this garden annually, most of it absorbed by plant roots. The rest flows into drains in the courtyard, which is also the flat roof of the college’s facilities building.
“So we’re slowing the water down, and cleansing it, rather than sending it into storm sewers,” said Mr. Schumacher, who graduated last year from Teachers College with a degree in elementary education. He started a vegetable garden with preschoolers in this same courtyard a few years ago, then landed a $10,000 grant from Brita with his proposal to build a rain garden here.
“I wanted to do a green roof, but the slopes are too steep,” Mr. Schumacher said, nodding toward the peaked roofs of the Gothic-style buildings surrounding the space.
College administrators approved the plan and contributed another $15,000, to repair drains under the courtyard and help pay for the garden, as well as to pay Alive Structures to replace the sickly potted yews with natives like dogwood and mountain laurel and to plant dwarf white pines along 120th Street.
Mr. Schumacher asked the Brooklyn firm to do the job because of its commitment to using native species, in both private gardens and public spaces.
“It seemed a nice match for what we’re doing here,” he said. Certainly he and Ms. Majorelle agree when it comes to bringing back bits and pieces of Mannahatta, that deep forest that covered the island before Henry Hudson came up the river 400 years ago. It’s very exciting to imagine Manhattan when there were hills and pine forests and marshes,” Ms. Majorelle said. “That’s what’s cool about this project: it feels like a river.”
They both are cognizant of the connection between native plants, many of which are endangered, and the wildlife they sustain. And Ms. Majorelle, whose company has installed 15 green roofs, is trying to spread native plants across as many roofs and concrete courtyards as possible.
“I put 20 plants of Asclepias tuberosa, or butterfly weed, on the green roof of our office, which is eight stories high, and the monarch caterpillars found them,” she said.
In building this rain garden in a courtyard, the Majorelles applied many of the same principles they use on green roofs. They knew from speaking with college administrators that the courtyard, where countless graduations and gatherings have been held, could bear the weight of the garden, with its three to four tons of stones, soil and plants.
The first step in constructing the garden was bending the dark-colored aluminum edging (GeoEdge, made by Permaloc) to mimic the undulating sides of a stream. To protect the concrete, they put a roof membrane on top of it, as well as a drainage mat to keep excess water from pooling on the surface.
The shape and size of the garden was constricted by the public gatherings in the courtyard. “Otherwise, I would have covered it with a pond,” Ms. Majorelle said. But those restrictions inspired the riverbed.
Mr. Majorelle worked with a friend who owns a metal shop to build a wide copper pan, angled just below the downspout, to send water gushing into the garden. They drilled a hole in the back of the downspout and attached a rubber tube; buried under pea gravel and rocks, it carries water to the second half of the garden.
“Our concern was that the water wouldn’t travel as far as it needed to go,” Ms. Marjorelle said.
It took their sturdy crew of four about a week to lug tons of gravel and sand, good topsoil, compost and river rocks up the dozen steps to the courtyard.
After the edging and protective mats went down, they spread a few inches of pea gravel over the surface of the space, nestled the water tube into the gravel, then covered it with more gravel and sand. Then hundreds of river rocks went on top, along with the boulders, some four feet wide, set in choice spots.
“We handpicked the rocks ourselves, from the Stone Center in New Jersey,” Mr. Majorelle said. “We didn’t have that big a budget, so we saved money by delivering them ourselves.
Getting It Rolling
Creating a rain garden in a city or suburban yard is easier than building one on a rooftop or in a courtyard, because water will drain more naturally into the earth below. The garden should be at least 10 feet from the foundation of the house, on a slight downward slope, or in a swale where water collects naturally. Connecting a pipe or hose from the downspout, digging the space to the proper depth (usually from 5 to 8 inches deep) and choosing appropriate plants are not difficult, but some planning and basic knowledge are required.
Several Web sites offer excellent information, including those of the New York State Department of Environmental Conservation (dec.ny.gov/public/44330.html), the Wisconsin Department of Natural Resources (dnr.state.wi.us/runoff/rg) and the West Michigan Environmental Action Council (raingardens.org).
“Rain Gardens: Managing Water Sustainably in the Garden and Designed Landscape,” by Nigel Dunnett and Andy Clayden, is a valuable guide for designing and building a rain garden.
A first-person how-to, “Rain Gardens: Using Spectacular Wetland Plantings to Reduce Runoff,” by Janet Marinelli, who built one with her husband, Don, on Shelter Island, is available on the Brooklyn Botanic Garden’s Web site (bbg.org/gardening/article/rain_gardens). The article includes links to other excellent online guides.