If you don’t know your trees very well, you might mistake this one for a sumac, ash, hickory, black walnut, butternut, or maybe a pecan. The distinction is more than superficial. Unlike those other fine trees, our mystery tree is an Asian import that has become a major pain in the buttski in much of the United States (and in many national parks) since it was originally introduced in Atlantic Coast areas in the late 1700s as a host tree for silk moths. This tree not only grows fast, spreads fast, and can live where other trees can’t, it also crowds out native vegetation, damages cropland, does wildlife little good, and is very difficult to eradicate. It even has a foul odor. Not surprisingly, some folks call it “the tree from hell.”
Our mystery tree is fairly attractive, though its beauty is only skin deep. Its bark looks somewhat like the skin of a cantaloupe. Its pinnately compound, fern-like leaves (10-41 leaflets) are large -- up to four feet in length -- and turn slightly yellow before they drop in the fall. This is a dioecious species, with male and female flowers on separate trees. Summer-flowering female trees are loaded with attractive terminal clusters of reddish-brown or tan single-winged fruits (called samaras), some of which persist through winter. The blossoms and broken or lacerated branches and twigs of the male tree have an unpleasant “nutty” odor reminiscent of rancid peanut butter.
This tree grows straight, tall, and often in dense, clonal thickets. It may top out at 80-100 feet under good growing conditions, and an exceptionally big one might have a trunk five feet in diameter. And boy, does this tree ever grow fast. It’s not at all unusual for one of these things to reach 50 feet or more in its first 25 years. It may live for 50 years or more too, though many succumb at a much younger age. Like nearly all fast-growing trees, this one is on the brittle side and subject to wind damage (not least because mature ones are usually hollow).
Being able to grow where other trees can’t is a signature trait. Though it especially likes disturbed areas that get lots of sun and have moist, well-drained soil, the darn thing will grow just about anywhere except in deep shade. Few places are too hot, too cold, too wet, too dry, too dusty, or too smoky for this tree. People who see it growing in sidewalks, alleys, gutters, parking lots, trash piles, and other improbable places in urban areas sometimes find it hard to believe their eyes. The damage this tree does to pavement and building foundations is very real, though.
Several of this tree’s traits assure its rapid spread. In addition to growing quickly, it reproduces both vegetatively (via suckering) and sexually (via seeds), suppresses competing plants with a toxin it secretes in its bark and leaves, and produces immense numbers of winged seeds (up to 325,000 per female tree) that have a high germination rate and can be carried long distances by wind or water, colonizing areas as much as two air miles distant. Humans have also transported the tree for landscaping and land reclamation purposes, taking it even to the Pacific Coast states.
Not surprisingly, our mystery tree is distributed very widely, being found in 42 states and considered invasive in at least 30 (see map). So far, 29 units of the National Park System have reported it as an invasive species. You can find it in all of the following parks, and probably some not listed here.
Delaware Water Gap National Recreation Area (PA)
Eisenhower National Historic Site (PA)
Gettysburg National Military Park (PA)
Antietam National Battlefield (MD)
Catoctin Mountain Park (MD)
Monocacy National Battlefield Park (MD)
Chesapeake & Ohio Canal National Historical Park (DC, MD, WV)
National Capital Parks East (DC)
Rock Creek National Park (DC)
Appomattox Court House National Historical Park (VA)
Blue Ridge Parkway (VA/NC)
Booker T Washington National Monument (VA)
Colonial National Historical Park (VA)
Fredericksburg & Spotsylvania National Military Park (VA)
George Washington Birthplace National Monument (VA)
Manassas National Battlefield Park (VA)
Petersburg National Battlefield (VA)
Prince William Forest Park (VA)
Richmond National Battlefield Park (VA)
Shenandoah National Park (VA)
Harpers Ferry National Historical Park (WV)
Great Smoky Mountains National Park (NC/TN)
Kings Mountain National Military Park (SC)
Indiana Dunes National Lakeshore (IN)
Stones River National Battlefield (TN)
Vicksburg National Military Park (MS)
Grand Canyon National Park (AZ)
Death Valley National Park (CA)
Yosemite National Park (CA)
Given the mystery tree’s potential, it’s likely that this list will soon be expanded.
Can you identify this “tree from hell”? Be sure to read tomorrow’s “Mystery Plant Revealed” for discussion and additional details.