Q. Is Fine Line Buckthorn (Rhamnus frangula) invasive in Chester County, Pennsylvania?
It certainly is an attractive plant, but it seems that it is invasive. Here is what I found about it. I hope it helps you make a decision.
Rhamnus frangula was probably introduced to North America about 200 years ago, and in Canada about 100 years ago. It was planted for hedgerows, forestry plantings, and wildlife habitat, but has become an invasive species, invading forests in the northeastern United States and wetlands and moist forest in the midwestern United States. It is predicted to continue to expand its North American range with time. Its invasiveness is assisted by its high adaptability and pollution tolerance.
It invades forests and grows in the understory in spots with a lot of light. These areas, usually where a tree has fallen, normally allow locally native tree seedlings to grow and eventually fill in the gap in the canopy. But when F. alnus invades and grows in these locations, its dense canopy prevents light from reaching the ground and therefore prevents other seedlings from growing. It tends to grow more densely and with larger individuals in lower topographical areas with moist, fertile soils, and is very problematic for land managers. Uplands forests are not invaded as easily as lower lying ones. Hemlock-oak stands, which tend to be older stands of trees, are much less suitable for F. alnus because the density of the tree canopy creates a shadier environment that is not as suitable for F. alnus. Eastern White Oak stands are easily invaded because they allow more light to reach the forest floor, and tree stands that are cut are very quickly invaded while undisturbed stands are rarely invaded.
Small saplings can be hand-pulled, but control of larger examples is best achieved using herbicides. F. alnus and the related species Rhamnus cathartica have been banned from sale, transport, or import to MInnesota and Illinois and It is considered invasive, but not banned, in Connecticut.