According to a 2010 survey conducted by the USDA, less than half of the plant life in the Chicago region is native to the area.
It's Joe Rothleutner's job, in part, to make sure the region's native plants are protected. He's the Morton Arboretum's tree improvement specialist, and he breeds new tree and shrub cultivars – plants grown for specific traits – to benefit the future of the Chicago area’s natural landscape.
His work at the arboretum’s New Plant Development Program covers the leafy spectrum, from cloning ornamental plants that produce beautiful flowers to cultivating cross-bred tree species resistant to invasive pests. He targets plants hardy enough to withstand Chicago’s harsh winter, urban pollution and the increasing effects of climate change.
According to Rothleutner, the biggest immediate threat to Chicago’s urban forest is undoubtedly the emerald ash borer. Since the June 2006 discovery of this wood-boring invasive pest in Illinois, millions of ash trees have been killed by the insect's burrowing larvae, which feed on inner bark.
“If your ash trees aren’t being treated with insecticide, they’re pretty much doomed,” Rothleutner said.
In 2005, 2008 and 2011, scientists from the Morton Arboretum and other public gardens made trips to north-central China to collect seeds of Asian ash trees that may have co-evolved with the invasive pest and developed a resistance to it. Rothleutner said the seeds have germinated, but any verdict on whether the plants could replace the area's fallen ash trees will take years.