Bittersweet Confusion

Some plants generate confusion.  Ask the man on the street to identify a pine or spruce, and you’ll find he’s confused the pine with the spruce.  When someone mentions a red maple, are they referring to a red-leaved Norway maple (Acer platanoides ‘Crimson King’), a red-leaved Japanese maple (Acer palmatum ‘Bloodgood’) or the true red maple (Acer rubrum)?  Often it is one of the first two, while choice three is best.  Only one thing is certain:  misidentification is a human issue.  No plant ever had an identity crisis.  Since they let it all hang out, it’s up to us to observe their attributes more closely before we attach a label to them.

Consider bittersweet, plants placed today in the genus Celastrus.  Early settlers to these parts thought a vine they came upon looked like Europe’s bittersweet, so they gave the new plant the same name.  Oops.  The olde worlde herbe turned out to be Solanum dulcamara or Eurasian nightshade, a completely unrelated species to our native American Celastrus scandens.  While the fruits of both look similar at one stage, the leaves, flowers and stems are night and day different. 

Jump ahead to the mid-1800’s.  While  American bittersweet was ornamental enough for gardens, chiefly valued for its fiery-orange fall fruit the shape of a pea, Oriental bittersweet (Celastrus orbiculatus) was thought to be better.  Some botanical wizard imported it from China or Japan into the northeast, and soon it was found to be better.  A better climber, since this new species not only scrambled up trees, but it could break, smother and strangle them (see photo, bittersweet taking on spruces).  A better propagator, too, since its fruit usually has five or more seeds, while the native’s berry often only contains one.  Since the release of the Oriental species, it has largely taken over the habitat of the American in New England and New York, and has possibly hybridized with it, too.

Straightforward enough.  We should banish the invader while aiding our hometown hero.  Unfortunately, for folks uninitiated in the nuances of bittersweet, the two types are tough to tell apart.  When someone asks which one they have on their land, it is a darn good question, one worth pondering before any further action is taken.

Start with flowers and fruit.  American bittersweet has these in clusters on the end of the shoot, while Oriental bittersweet has flowers and fruit all along the stem.  American bittersweet has an orange capsule that encloses the fruit, while Oriental’s are yellow.  American’s fruits are larger, but contain few seeds, as noted above.

That’s great, but there’s another rub:  both species feature separate male and female plants.  Male plants don’t make berries, so those clues are out.  So get out your magnifier, because male American flowers make yellow pollen while male Oriental flowers make white pollen.  There is also a vegetative indicator.  When American vines leaf out in spring, the leaves are rolled like a scroll, while Oriental’s are folded just once. 

Confused?  Check the internet for the Great Lakes Science Center Fact Sheet 2007-2: https://www.fs.usda.gov/Internet/FSE_DOCUMENTS/fsbdev3_017307.pdf