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“American elm is a foundation tree species in floodplain forests,” says Leila Wilson, an ecologist with the U.S. Forest Service. “They are facing severe threats from non-native pests and pathogens…” Wilson knows these trees well. Each one comes from a seed she harvested from a tree whose flowers she isolated with little plastic bags, then hand-fertilized using pollen collected in the lab. … “We’re going to be infecting them with the Dutch elm disease fungus,” she says as she drills the first hole. …She and her colleagues will look for survivor trees by rating the lushness of their canopies. …The ones that survive will have their seeds harvested to be used to grow a nursery stock that can be planted as part of floodplain restoration projects around the region.