Collected on September 8, 1991, this specimen was found near Tarentum, Pennsylvania by Walt Zanol.
If you had to pick the most aggressive, invasive plant in the Pittsburgh area, knotweed would be among the top choices. This particular specimen is Bohemian knotweed (Fallopia xbohemica), a hybrid between giant knotweed (Fallopia sachalinensis) and Japanese knotweed (Fallopia japonica). Japanese knotweed was introduced from East Asia, and giant knotweed came from Sakhalin (Russia). The hybrid likely originated when these two species met after they were introduced in Europe.
Both species and their hybrid can be found around Pittsburgh, often in enormous dense clusters along highways and waterways. Take note on your drive to work or walk in the neighborhood—knotweeds are all around!
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