Plant Collecting in the Neighborhood

Kim Shearer is not only curator of collections at The Morton Arboretum, but also an avid rock climber. One day a few years ago, on a trail near a favorite climbing spot in Wisconsin, she noticed an interesting plant: mountain maple (Acer spicatum), which she knew from the Appalachian Mountains.

“The Appalachians are incredibly old,” she said. It was striking for Shearer to see a tree species she knew from that ancient mountain range growing in the Upper Midwest, where most forests are much newer because glaciers covered much of the land until just 10,000 years ago. Yet Shearer knew this spot, Devil’s Lake State Park, was in an area of Wisconsin that the glaciers had missed.

She suspected that mountain maples growing here might have a distinct genetic legacy that could contribute to useful and resilient plants for city and suburban landscapes.

So this year, Shearer assembled an all-woman team (a rarity in plant collections), including Katrina Lewin, plant records coordinator; intern Selu Adams; and Gabi Rodriguez, plant labeling coordinator at Chicago Botanic Garden. Their expedition was funded by the U.S. Department of Agriculture’s Plant Exchange Office.

Together, they made the three-hour drive several times during the growing season to collect mountain maple seeds as well as other native trees and shrubs, including sugar maple, black maple, serviceberry, basswood, and bush honeysuckle. These are familiar plants that are already growing in the Arboretum’s collections, as well as in many public and private gardens. Why, then, collect more specimens of them from three hours away?

“Different populations of plants growing in isolation from each other can develop different adaptations,” said Shearer, who oversees the Arboretum’s Daniel P. Haerther Charitable Trust New Plant Development Program, as well as its collections.

If the Arboretum’s collections include a wide range of genetic diversity from multiple populations of each species, she said, “We can use that to make sure our collections are resilient and also to develop new cultivated varieties of plants that are useful in cities and suburbs.”

Some of the qualities the new plant development program works toward are winter hardiness; drought tolerance, to withstand the weather extremes of a changing climate; and easy propagation and production, so nurseries can grow plants in great enough quantities to be planted widely.

“A lot of the native plants we would like to see in the landscape are not as vigorous or as easy to grow as they need to be to thrive in cities and suburbs,” she said. Sugar maple, for example, is beloved for its fall color, but not at all drought-tolerant.

“We want to contribute to developing more useful qualities in these plants by expanding the diversity of our collections,” Shearer said. “We need a broad genetic base.”

She is chair of the USDA’s Woody Landscape Plant Crop Germplasm Committee, which identifies vulnerabilities and threats to tree and shrub species as well as research priorities.

Collecting plants from the woods off the crowded trails in Wisconsin’s most popular state park, with 2.5 million visitors a year, may not seem like the same kind of challenge as other Arboretum expeditions to remote parts of China, Korea, and the Republic of Georgia in search of rare and endangered plants. Yet seeing the potential in plant populations and collecting them in a way that preserves their scientific value takes the same kind of deep tree expertise everywhere.

For the Arboretum, finding valuable native plants in its own backyard is nothing new. Throughout its history, it has gathered plants from all over Illinois and nearby states, growing along roadsides and train tracks, and in parking lots and cemeteries, as well as parks and forests. Some collected specimens have grown to become stately trees along the Arboretum’s trails. Others are dried and preserved in the Herbarium, adding to a rich record of which plants grow where in the Chicago region and other parts of the world.

This winter, mountain maple seeds collected from Devil’s Lake will be safely stored until they can be grown in greenhouses under the care of the Arboretum’s expert propagation staff. In years to come, they will be tested, evaluated for useful qualities, and shared with other institutions. Shearer hopes they will contribute to the beauty of the Arboretum’s grounds, the resilience of the collections, and the development of lovely, sturdy, hard-working plants that can thrive where people live.