www.MichiganGardener.com | May 2013 | Michigan Gardener
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Bob Grese’s garden pictured through the seasons…
Bob Grese
Near the house, the prairie plantings transition to woodland species. In spring, as new plants are emerging, Grese picks the weeds while they are still seedlings in what he calls “just-intime weeding.”
though I didn’t know a field such as this existed at the time,” he remembered. Grese purchased this Ann Arbor house and city lot in 1988 as a fixer-upper with a garden in mind. “I loved that it was set back on the lot with a good southern exposure for a garden in the front. I was looking for a place where I could experiment with designing and growing a prairie garden. The house needed a lot of work, but I liked that I could tailor a redesign of the house to my own interests and lifestyle. We remodeled again in 2004. We were also excited about the prospect of adding a green roof on the garage so I could trial native plants adaptable to green roof plantings,” Grese recalled. The earliest gardens were a prairie garden near the street, woodland near the house, vegetable garden on the west side, and more woodland in the rear. After the 2004 remodel, the vegetable garden on the west side was eliminated and a new walkway was built along the garage. Later, they re-routed their sump pump to empty into a rain garden created in the front woodland. The overflow from a rain barrel and green roof also drain into this space. In 2009, Grese removed a section of prairie and planted a front vegetable garden. As the oak and hickory trees in the front have grown, the prairie garden is evolving into an oak savannah with fewer grasses and more shade-tolerant forbs (herbaceous flowering plants other than grasses and grass-like plants). Grese described his favorite spot in the garden, “We love sitting on the front porch and looking out to the street over the woodland garden, especially in the early spring and summer. Fall is also a special time of great color from the diversity of shrubs and the goldenrods, asters, and grasses.” Grese spends a lot of effort to make sure his plantings are not mistaken for weeds. “My biggest challenge has been to insure that the wilder plantings show signs of being cared for. This means selective cutting of plants that become too tall
Summer near the house. As time passes, three main trees (basswood, bur oak, and shagbark hickory) are producing more shade and changing the plants that thrive in the garden.
The same view in the fall. Autumn colors and late-blooming native plants characterize the scene.
Bob Grese’s green roof project In 2004 the Greses decided to remodel their house. Bob Grese recalled, “We decided to rebuild the garage with a green roof. At the time, I was intrigued with green roof technology and wanted to experiment with native plants that would thrive in shallow soil mixtures and dry conditions.” The green roof consists of several layers. Oversized joints are used for the extra weight of soil, plants, and moisture. Three-quarter inch decking is topped with hot asphalt sealant for waterproofing. Next is a pre-formed plastic drainage layer and above that is a root barrier. The soil consists of expanded clay, shale, sand, and 5 to 10 percent organic matter. The 4- to 6-inch deep soil is held in place by aluminum edging. A one-foot strip of washed ballast rock frames the roof edge. The roof slants one-quarter inch per foot to the east for drainage into a standard gutter and rain chain. Grese explained the plant choices, “In considering plants for the roof, I explored lists of green roof plants and several types of habitats. I started with about 35 species, a quarter of which were native grasses and sedges, and the rest forbs (herbaceous flowering plants other than grasses or grass-like plants) and broad-leaved plants. I used locally-collected seed where available, including nodding onion (Allium cernuum), pussytoes (Antennaria parlinii), columbine (Aquilegia caor staking plants that would tend to fall over. I have included “Wild Ones” and “National Wildlife Federation Certified Wildlife Habitat” signs near the front sidewalk to explain to visitors that my wild garden is intentional,” explained Grese. Other maintenance includes raking leaves and grinding them into mulch for the woodlands and vegetable garden beds.
nadensis), Bicknell’s sedge (Carex bicknellii), purple lovegrass (Eragrostis spectabilis), and little bluestem (Schizachyrium scoparium). Others I secured from Wildtype Native Plants and Native Plant Nursery. These were flowering spurge (Euphorbia corollata), northern bedstraw (Galium boreale), prickly pear cactus (Opuntia humifusa), and prairie dropseed (Sporobolis heterolepis). I also harvested a few plants from my front yard prairie, especially wild strawberry (Fragaria virginiana).” The plants have generally done well and there are very few weeds. The green roof cools the garage in summer, and filters and absorbs rainwater. It offers a more pleasant view from their bedroom window with the changing textures and colors of the seasons. After the plants’ original establishment, Grese did not water for several years. During occasional 100-degree temperatures, however, he was forced to water once a week or the plants would go dormant or even die. The mix of plants has changed over the years as some have disappeared completely, some have temporarily gone dormant, and others have expanded. “I see great value in a green roof system that is modeled after native ecosystems with much built-in resiliency,” Grese affirmed. Grass and forb “thatch” (a build-up of garden leaves, stems, and debris) from the prairie area is used as mulch on paths and around vegetable plants. At the end of the season, this mulch is worked into the soil. Every couple years, Grese conducts a continued on next page