When people think of trees to plant for fall color, they automatically think of maples. They are no doubt influenced by countless calendars whose October page features New England sugar maples and red maples blazing with color. However, the overplanting of maples in Oregon and their susceptibility to a lethal pest are good reasons to pick alternatives. Homeowners who do can enjoy brilliant autumn color while reducing their community’s vulnerability to catastrophic tree loss, according to Oregon Department of Forestry officials. In most Oregon cities and towns, maples are overplanted at levels considered highly risky by urban foresters. For example, Portland’s comprehensive street tree inventory completed in 2016 showed that maples dominate the city’s streetscapes, accounting for more than one tree in four. That percentage is well above an emerging consensus among urban foresters that communities should avoid having more than 10 percent of their trees belong to a single genus and no more than 20 percent in any one tree family. The risk, according to ODF Urban and Community Forestry Program Manager Kristin Ramstad, is from introduced pests that find an abundant food supply in streets and yards planted with lots of the same type of tree. For maples, the peril comes from the Asian longhorn beetle. “There have been a number of accidental importations to the U.S. of this beetle, which attacks and kills maples of all kinds, as well as horse-chestnut, poplar and willow,” said Ramstad. “So far the only remedy to stop the beetle is to cut down and chip or burn all maples and other susceptible tree species within a wide quarantine zone.” Ramstad said white ash (Fraxinus americana), with amazing red to reddish-purple fall color, used to be a recommended alternative for maples as well as for elms wiped out by Dutch elm disease. But the rapid spread since 2002 of emerald ash borer, which is universally fatal to ash trees, makes ashes of any kind no longer a wise choice.
