Goodhue County Extension Master Gardener Genella Mussell
answering questions about invasive Oriental Bittersweet
by Genella Mussell, Goodhue County Extension Master Gardener
As leaves, trees and undergrowth begin to fill out and eventually paint our world green I want to remind folks to be on the lookout for invasive species. We have heard the awful news about the Emerald Ash Borer for our Ash trees. How many of us as gardeners are aware of Oriental Bittersweet?
Bittersweet? That beautiful berry and vine used to make those fall wreaths often seen at craft fairs and stores? Well, yes and no. The bittersweet that should be used in these wreaths is the American Bittersweet. Unfortunately there may be wreaths made with a variety named Oriental Bittersweet.
The bittersweet causing concern for the Minnesota DNR is the Oriental Bittersweet. Unfortunately it was introduced to the US as an ornamental vine. It is a climbing woody perennial vine. It has proven to be very aggressive. It can grow to heights of 66’. Because of this aggressive growth it can smother trees, shrubs and other vegetation. It had been known to cover entire trees and pull them down due to the heaviness of the growth. The vines can girdle and kill grown trees.
The Oriental Bittersweet looks very similar to the American. Differences that can be noted are in how the fruit and flowers grow and the color of the berries. The Oriental Bittersweet has fruit and flowers located in the leaf axils along the length of the stem. American bittersweet, however, only has fruit and flowers in terminal clusters. The berries of the American Bittersweet are orange and those of the Oriental yellow. These are best seen in the fall.
Why the warning? As stated, this vine is very aggressive. The Oriental Bittersweet has at present a limited distribution in Minnesota, which is why we need to stop it now. As gardeners we should be on the lookout for it or at least aware of it. Because it is a favorite in ornamental wreaths it may be unintentionally introduced. So as a warning, when attending craft fairs or shows, take a careful look at the wreath and make sure they are not compromised of the Oriental Bittersweet.
Sadly, we have any number of invasive species of which we must be aware. If we take a moment to familiarize ourselves with the plants around us or those with which we may come in contact, we can perhaps slow the spread of some of these species. We should remember the old adage, “An ounce of prevention is worth a pound of cure”.