Oaklyn Library Roof is a Prairie
EVANSVILLE — Hot evening sun spilled over a riot of wildflowers, insects droned and flocks of goldfinches nibbled on patches of seeding bee balm as librarian Pam Locker and Dr. Chris Hochwender of the University of Evansville walked the paths of the native prairie reconstruction at Oaklyn Branch Library on Oak Hill Road.
Hochwender, who specializes in plant-herbivore interactions and teaches Environmental Science, Evolution and Ecology, and Ecology at the University of Evansville, was there to help identify native and invasive plants in the meadow. Master gardener Locker was taking note of species and varieties new to her.
The meadow was built as an adjunct to the library building’s “green roof,” a portion of the building actually covered with a carefully managed layer of soil and grass.
“We had the land for the new library, and there were two possibilities of how to build because of the slope,” said Locker. “Either put the building at the bottom of the hill, or put it into the side and have the green roof.”
Locker said the building was designed by architect Bill Brown, who is now director of sustainability at Indiana University.
“He’s a green guy and had an interest in building a green building,” she said. “Now the energy bills are very efficient, and the roof will last the life of the building, so there is less maintenance. Along with the green roof, they decided to do a native prairie reconstruction around it. It was an ambitious effort, but it has succeeded.”
The library opened in 2003, but the meadow didn’t take off right away, Locker said.
“It’s really hard to start a native meadow because there are so many weed seeds in the soil,” she said. “They hired Eco Logic from Bloomington to come look at it, and they used Roundup to basically kill everything, and then used a special seed drill to plant the native seeds. It’s been going well for eight years now, and each year we get more of the good things, and they take over and outweigh the bad things. ... It’s a process of keeping after the bad things until they are all gone.”
The caretakers of the meadow are constantly removing invasive plants such as thistle, ragweed, hairy vetch, various vines such as morning glory, Johnson grass, white sweet clover, yellow sweet clover, Queen Anne’s lace and volunteer trees, especially cottonwood. These might be pretty, but are not native to North America and will take over the habitat meant for indigenous plants.
The meadow is weeded in spring, early summer and fall.
“We did a total of probably 40 hours worth of weeding earlier this year,” Locker said. “The red clover isn’t something we want, and we had to pull out sweet peas, and lots of crown vetch. That’s bad because once it gets in it produces so many seeds. Queen Anne’s lace can get very invasive, too. If you can at least get the seed heads off the invasives before they spread, it’s better than nothing. “
“Most of the desirable native plants in the meadow fit into a few families,” Hochweder said. “There’s the mint family, the pea family, the aster family and the grasses.”
Members of these families not indigenous to North America can be invasives as well, of course, and it’s important to be able to identify which are which.
Hochwender said that in the wild, prairie settings do not get mowed, of course, and dead growth falls over and forms a layer under the new green growth. Every few years, lightning starts a fire, and this dry, old growth burns quickly. This is how prairies are cleared and renewed. Because burns wouldn’t be prudent at Oaklyn, the meadow is mowed once a year, in November, to keep trees from taking over.
“The meadow of course changes so much with the seasons,” said Locker. “Visitors are welcome to come inside the building to pick up a brochure, as well as to walk the mown paths.”
In the meadow in spring you’ll find hairy mountain wood mint, beard’s tongue, purple prairie clover, butterfly weed, baptisia (wild indigo) and swamp milkweed among others; early summer hosts milkweed and bee balm; and in the fall various native goldenrods, New England aster and dogbane abound.
Some of the most prominent late-summer-blooming plants in the meadow now are:
Gray-headed coneflower — Ratibida pinnata: These pretty yellow flowers are the most abundant in the meadow in late summer. They resemble black-eyed Susans at a glance, but have a more prominent central button and petals that are less disklike and droop around the stem like the skirt of a bright yellow dress. According to Illinois Wildflowers, this very hardy perennial is native to most of the Eastern United States and is especially attractive to bees.
Cup Plant — Silphium perfoliatum: These tall (4 to 10 feet) plants with sunflowerlike flowers are unusual in the wilds of Southern Indiana, although common to true prairie areas. Some wild stands can be seen on U.S. Interstate 64 headed toward St. Louis. According to illinoiswildflowers.org, the cup plant sends down a large taproot deep into the soil, while branching rhizomes near the surface quickly turn one plant into a colony. The plant’s name is derived from the shape of the leaves, which join to form a deep, water-collecting cup around the central stem.
Rattlesnake Master — Eryngium yuccifolium: This plant is an unusual member of the Apiaceae or Umbelliferae family, which contains carrots and parsley and is usually characterized by flat-topped umbels, as in Queen Anne’s Lace. According to the Missouri Botanical Garden, it was a common plant in tallgrass prairie of the Midwest. Its name comes from its onetime use as an antidote to rattlesnake venom. The plant can grow to 4 or more feet tall. The leaves of the tough basal rosette resemble yucca.
Prairie Coneflower or Mexican Hat — Ratibida columnifera: According to wildflower.org, this small coneflower grows only from 1½- to 3-feet tall. Petals can be solid yellow, solid rust-red, or, as at Oaklyn, a combination. It is named for its resemblance to a tall, colorful, Mexican sombrero, and naturally grows in prairie settings from British Columbia to Mexico, east to Illinois, and has spread from Alabama to Wyoming and from New Jersey to Colorado.
Eastern Purple Coneflower — Echinacea purpurea: This is the echinacea plant famously drunk as a tea to build the immune system, and is also a favorite landscaping plant for its long stems and bright purple color. According to wildflower.org, all echinacea flowers were named after the hedgehog, “echino” in Greek, because the central, prickly, brown part of the flower resembles a curled-up hedgehog.
Butterfly Weed — Asclepias tuberosa: This member of the milkweed family, native to the Eastern United States, is called butterfly weed because its bright orange color and abundant nectar will draw bees, butterflies and hummingbirds. According to wildflower.org, this perennial forms a large underground tuber and re-sprouts from it each spring. Unlike most milkweeds, no milky sap oozes from this plant when broken. Another name for this plant is pleurisy root, because it was once used to help sooth pleurisy and other pulmonary problems.
Black-eyed Susan — Rudbeckia hirta: Black-eyed Susans are native to almost every state except Hawaii. According to the University of Texas, depending on the variety and location, these hardy and prolific bloomers of late summer may grow as annuals, perennials or biennials.
The Oaklyn Meadow has been adopted as an official Garden Project by the Southwestern Indiana Master Gardeners Association, and it and the Southwestern Indiana Native Plant and Wildflower Society help with maintenance and improvement of the meadow.
The Oaklyn green roof won a Green Roofs for Healthy Cities North American Green Roofs of Excellence Award in 2004. It has been given accolades in two books about green roofs: “Award Winning Green Roof Designs,” by Steven Peck, and “The Professional Guide to Green Roofs, by Karla Dakin,” Lisa Lee Benjami