Tree-of-heaven has branches containing multiple leaflets, like those pictured here.


In this area one has probably seen many of the non-native invasive plants that have gotten out of control and taken over the landscape — Japanese knotweed, bush honeysuckles, and multiflora rose to name a few.

Because these plants have been left untreated for so long, they dominate a large part of our stream sides and forests, and controlling them can seem like a daunting task. In fact, invasive plant control costs tens of billions of dollars a year across the U.S. Most invasive plants produce a great number of seeds annually, and can spread quickly. But if these plants had been recognized and treated early, it would have saved much time and effort, and preserved the landscape.

The best approach to stopping invasive plants is to prevent them from coming into a new area in the first place. There are several easy steps one can take to prevent the transport of invasive plants from one area to the next. In fact, the main pathway for spread of invasive plants is by transportation of their seeds by humans. Seeds that get deposited in the soil then get trapped and transported in tires, equipment, and even the tread in one’s shoes. So when people are out recreating and enjoying nature or working in an area known to have invasive plants (which is most places these days), make sure to inspect and clean equipment, recreation vehicles, car tires, and yes even boots and pants before travelling to a new place.

The second best approach to stopping invasive plants when they do get into a new area is to catch them early and treat them before they can reproduce. This approach, called Early Detection and Rapid Response, or EDRR for short, can be an effective way to prevent many of the invasive plants that are creeping into this area from becoming another big problem. Anyone can help in this fight. It simply requires that one watch out for these plants — when out for a hike, getting a boat into the water, or even just enjoying one’s own property. If caught early, many invasive plants can be controlled mechanically by simply pulling them out.

There are many potentially invasive plants in or near the area that one should be on the lookout for. One well known invasive tree that is on the fringes of the area, having been detected in Cameron County to the southeast and Warren County to the west, is Tree-of-Heaven. This tree looks very similar to native sumacs, with its compound leaves and greyish bark. The best way to distinguish it from a sumac is actually with the “smell test.” When the leaves of Tree-of-Heaven are crushed it has a very distinct odor that some describe as rotten peanut butter. This tree produces over 300,000 seeds per year and also spreads by root suckers (small stems that develop off the root system), so early detection is critical. One is most likely to first see it along roadways or disturbed, open areas. Small seedlings can be pulled, but larger stems might require chemical treatment to control the root system.

Several of potentially invasive plants are ornamentals residents may have in backyards that can escape into the wild. One such plant is burning bush, a popular bush planted for its brilliant red foliage in the fall. Unfortunately, this plant has also been known to escape the backyard and take over forests. While not problematic in this area yet, it is considered a serious threat in other northeastern states — to such a degree that its sale has been banned.

To learn more about ‘weeds to watch’ one can check out the Pennsylvania Department of Conservation and Natural Resource’s “Watch List” online…and in a later article in this series on invasive plants, learn more about native alternatives for some of the ornamental plants that are problems in this area.

For more information contact Kimberly Bohn, Penn State Extension Educator at or 814-887-5613 or the McKean County Conservation District at 814-887-4001.