June 14, 1965: 54 years ago

Not all bittersweet vines are invasive to Pennsylvania. This specimen was collected on June 14, 1965 by botany curator Leroy  Henry  in Clearfield county,  along  Rt 969. American bittersweet (Celastrus scandens) is a woody vine that  blooms in June, which turn to beautiful clusters of orange/red fruit in late summer/fall.  The species is native to eastern USA, found along open thickets/edge of woods.

American bittersweet (Celastrus scandens) might be easily  confused with the much more common Asian bittersweet (Celastrus orbiculatus).  There are two major visual  differences between the species: 1) flower/fruit --  native species has single terminal cluster of many flowers/fruits at tips of branches, whereas the invasive has flowers/fruits at axils of leaves (where leaves connect to stem; and 2) leaves -- native  species' leaves are more elongate, whereas the invasive species' leaves are more round, often even circular ('orbiculate').

American  bittersweet is no longer common in Pennsylvania, most likely taken over by the closely  related Asian bittersweet.   Asian bittersweet  is a relatively newer addition to the  flora of Pennsylvania, not showing  up  in  western PA and  the  Pittsburgh region until  the 1980s.  Given its abundance and distribution throughout the region  now,  it is hard to fathom it was not present only several decades ago.

Research over the past decade has shown that the invasive species hybridizes with the native, likely contributing to  the decline  of the native American bittersweet.

Keep a look out for American bittersweet in our region.  (I have  not  seen it in Allegheny county, although we have historic  records)

This specimen image is now publicly available online:
http://midatlanticherbaria.org/portal/collections/individual/index.php?occid=12131436&clid=0