Plants, Not Plumbing

Monday, October 26th, 2009

Invasive species can threaten any ecosystem. In the rain gardens that K-State landscape architecture students planted last summer at Manhattan’s Sunset Zoo, the most resilient invaders have been the park’s itinerant, jewel-toned peacocks and their mates.

“I’ve spent some time chasing peafowl around, but I knew it wasn’t going to do much good, so I focused on planting, watering and weeding,” said Lee Skabelund, assistant professor of landscape architecture, who oversaw the project.

Despite the birds’ appetite, the installation on the hillside north of the President’s Garden already has cured one of the eroding site’s chronic problems. Sediment no longer turns the sidewalk’s lower reaches into a mud slick, and native prairie plants are surviving in the formerly compacted soil.

“It hasn’t been in the ground two months, and it’s paying dividends already,” said zoo director Scott Shoemaker in mid-summer 2009, who also participated in previous service-learning projects with K-State’s College of Architecture, Planning and Design.

Team members with the national zoo accreditation body noted the installation when they visited in early July, Shoemaker said. The Groundwater Foundation, a Nebraska non-profit, also mentioned the garden when renewing the zoo’s certification for 2009.

“It speaks to our conservation and environmental message,” Shoemaker said.

Rain gardens, a balancing act between topography and plant selection, hold rain where it falls, rather than channeling runoff into pipes and holes in the ground. “Plants, not plumbing,” are the solution for many sodden or eroded sites, Skabelund believes.

Reducing runoff also reduces pollution downstream, as well as controlling the cost to cities for storm-sewer installation and water treatment.

The zoo gardens’ stair-step arrangement of shallow depressions, limestone walls and curved planting beds may resemble an ambitious childhood bio-engineering experiment, but it is the result of careful analysis and design. The unusually wet spring and summer have provided a good test, Skabelund said.

This installation grew out of designs by Emily King of Brentwood, Missouri, and Lee Adams of St. Joseph, Missouri, during fall 2008. Andy Schaap of Abilene and Chris Enroth of Manhattan, who took Skabelund’s advanced planting design course in spring 2009, adapted and implemented those designs. More than a dozen volunteers, including master gardener Gregg Eyestone and students from K-State and Manhattan High School, got their hands dirty on site.

The plants, 25 native Kansas species, are still settling in among the shredded mulch, which is why any visit to the garden with Skabelund will gradually turn into a weeding session.

“The idea is, once it gets established, zoo personnel will just have to do a little weeding,” Skabelund said as he tugged at a weedy grass embracing an infant prairie dropseed. “And they’ll be able to mow along the edges.”

Easing maintenance is key to success for any garden, he said, not just at the zoo, where the sole horticulturalist is a half-time position. “If you don’t plan for maintenance concerns, your design is not going to last.”

Once the prairie grasses mature, informal terrace walls of tumbled limestone will provide alternative paths and places to sit. Right now, positioned as dams to slow runoff, they curve like dinosaur spines among the plantings.

At first, Shoemaker expected the rain garden to remain a class exercise, “but Lee really pushed to make it a reality.” In mid-September Shoemaker noted that after every hard rain he walks down to take a look at the rain gardens and finds that they are working just as they should, absorbing the rain and slowing stormwater runoff.

“Working on paper is OK,” Skabelund said, “but I wanted a living place that people could learn from. It became clear to me that the zoo was the place to do it as a design-build.”

Funds came from a Water Quality Restoration and Protection Service Learning grant awarded to K-State by the Kansas Department of Health & Environment using federal EPA money.

Skabelund and his students had considered other parks and schools around town, but none combined the security and readiness of the zoo site, along with its challenges: A slope, discharge from power-washing, two winding concrete sidewalks, and bare sandy earth compacted by passing zoo vehicles.

“Aesthetics and education opportunities in this context become critical,” Skabelund said. “You have tens of thousands of folks coming here every summer.”

Allie Eskew Lousch, Sunset Zoo’s Marketing and Development Officer loves the results. “It is a pleasure to walk through the garden. It is beautiful.”

As with the zoo’s sensory garden, hummingbird garden and butterfly garden, Shoemaker hopes rain-garden visitors will go and do likewise.

“We always try to convince people that these are things they can do in their back yards,” he said. (See accompanying story on do-it-yourself rain gardening.) Signs have been designed and installed to encourage as well as educate.

Looking to the prairie for solutions to urban problems requires adjustment, in engineering departments and in people’s heads. Skabelund quotes landscape architect Joan Iverson Nassauer about the need for “messy eco-systems in orderly frames.”

“People have expectations of what a garden should look like,” Skabelund said. “I’d like to deepen that perception. It’s necessary from an ecological and a financial point of view to consider using stormwater as a benefit in every place we interact with the land.”

SIDEBAR:

Grow your own solution

Lee Skabelund, assistant professor of landscape architecture at K-State, advises those who would start a rain garden at home to analyze their sites thoroughly before picking up a shovel. Take advantage of this summer’s thunderstorms to plan for next spring.

— Know where the water is coming from and where it goes. Take an umbrella outside and just watch. Are your downspouts the only stormwater source, or do neighboring streets and properties contribute? The volume of water determines the size and therefore the practicality of a rain garden.

— Rain gardens “hold the water where it falls,” Skabelund said, so that after the storm, rainwater gradually soaks in or evaporates. Your garden will consist of shallow depressions, not ponds, so earthmoving can be minimal.

— Concerned about raising mosquitoes? Look to the standing water in your gutters and outdoor drains before accusing your rain garden. Mosquito need four days of standing water to reproduce, Skabelund said. A properly designed garden won’t allow that.

— Locate plants according to their moisture tolerance and sunlight needs. Sedges thrive in areas that retain moisture between rains, while stiff goldenrod is a dry-site plant that can adapt to the wet. Expect to lose a few plants. “In siting species, it’s always a little bit of an experiment,” Skabelund said.

— Skabelund uses shredded hardwood mulch for new gardens, not wood chips, which float away during rainstorms. Shredded mulch knits together to protect plants and soil.

— He also avoids black plastic, landscape cloth and perforated “weed barriers,” which add expense and often become eyesores.

— At Sunset Zoo, the gardens are designed to mimic a Kansas prairie, for ease of maintenance and fitness within the Flint Hills. One source of native grasses and wildflowers that tolerate many soil types is Kaw River Restoration Nurseries in Lawrence, supplier of plants for the Sunset Zoo rain gardens.

— Native gardens won’t need much mowing, but weeding is critical, particularly early on. “Even with perennial gardens, the ones that look the best got a lot of attention.”

— Good primers on rain gardening include “Blue Thumb Guide to Raingardens,” by Rusty Schmidt et al, and the following on-line sources:

http://faculty.capd.ksu.edu/lskab/KSU-LARCP_Rain-Garden-Guidebook-lrs.pdf

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Plants, Not Plumbing