If you go down by the Susquehanna River you can see just how extensive the buckthorn invasion is, since most other trees have dropped their leaves but buckthorn hasn’t, so you can see the extent of their hold. They look harmless but they are not. Here’s a nice summary from Wisconsin:
Common buckthorn (Rhamnus cathartica)
Tall understory shrub or small tree up to 20-25’ tall, often with several stems arising from the base, and spreading crown. Gray to brown bark with prominent light-colored lenticels. (Caution: native plums and cherries have a similar bark). Plants are either male or female. Cut bark exposes yellow sapwood and orange heartwood. Twigs often end in stout thorns.
Common buckthorn is Restricted (Orange counties)
Other names for this plant include:
- Common names: Carolina buckthorn, European buckthorn
- Invades oak forests, riparian woods, savannas, prairies, old fields, and roadsides. It thrives particularly on well-drained soils.
- Common buckthorn has a broad environmental tolerance. It leafs out very early and retains its leaves late into the growing season, giving them a longer growing season than native plants.
- Creates dense shade, eliminating regeneration of tree seedlings and understory species.
- Allelopathic; produces chemical compounds that inhibit the growth of other vegetation.
Classification in Wisconsin: Restricted