The Climbing Strangler of Trees – Oriental Bittersweet

As a wanderer of forests, paddler of rivers, and hiker of hills I am always on the lookout for invasive plants. Over the past several years the spread of invasive plants has imperiled our native plants. Without the balance of competition from their native lands, these invasive plants spread over a wide area, displace our native plants and reduce the biological diversity of our forests and wetlands. In previous columns I have shared information on Japanese barberry and winged euonymus (burning bush). Today we’ll explore the tangled mess that is oriental bittersweet.

The first time I encountered oriental bittersweet (Celastrus orbiculatus) was when I lived in Woodstock. I discovered it vining up through a large rhododendron in our front yard. At first I would snip the vine at the ground level only to find it growing back and into the bush. Then I started pulling it up by the roots and yet it still seemed to magically grow back and up through the rhododendron.

Our property in Woodstock was a little more than an acre with most of it sloping straight uphill from the house into thick woods and brambles. Due to the steep incline we didn’t use the woods that much, though my son built a small wooden fort there one year. One day he invited me up to his fort and that was when I encountered oriental bittersweet yet again — and lots of it!

One of the tall white pines at the top of the hill was completely entangled with the vine. It had twisted and climbed more than 40 feet up the trunk and encased the branches. The base of the vine coming out of the ground was at least 4 inches in diameter. The snake-like constriction the vine put on the tree was one of the more gruesome sights I have seen in the plant world.

Since those early encounters I have done battle with Celastrus orbiculatus and my guess is many readers of this column have done the same.

Oriental bittersweet was introduced to the U.S. from Eastern Asia in the 1860s as an ornamental vining plant. By 1916 it was found in Connecticut and today is found throughout the state.

When it comes to understanding invasive plants in Connecticut and how to control them, my go-to source for expertise is the Connecticut Invasive Plant Working Group (CIPWG) at UConn. They have a great website full of information at http://cipwg.uconn.edu and the following is some basic information on oriental bittersweet from their website:

Oriental bittersweet is a deciduous woody vine that can reach 60 feet in height, and can grow to 4 inches in diameter. Its leaves are simple and alternate. It blooms in May with small yellow-green flowers, and its numerous green berries turn red in yellow capsules upon maturity.

Oriental bittersweet is a serious threat to plant communities due to its high reproductive rate, long-range dispersal, ability to root sucker, and rapid growth rate. Climbing vines severely damage or kill trees and shrubs by constricting and girdling stems, and by blocking sunlight.

Oriental bittersweet has a wide range of habitat preferences including roadsides, thickets, young forests and dunes. It is shade tolerant, readily germinating and growing under a closed forest canopy. Seeds are dispersed readily by birds and small mammals.

Here are a few of the management options suggested by CIPWG.

Hand Pulling:  Control can often be accomplished by hand-pulling for small populations (less than 1/4 acre). Plants pulled early in the season are much smaller and easier to manage. At my property in Putnam I find small vining shoots of oriental bittersweet along the stone wall adjacent to the house and in some of our perennial gardens. In the early spring when it first appears and the ground is soft, it is easy to pull up. It is important to pull slowly so the root doesn’t break off. The root has a distinctive orange color.

Cutting & Mowing:  Mowing (or brush hogging where woody plants are present) is suited to non-rocky, open areas that are not too steep for the equipment. Equipment should be cleaned prior to being brought to the site and should be thoroughly cleaned of all seeds and plant parts before leaving the site. I maintain our back horse pasture by mowing (brush hogging) to keep the weeds down. If I find oriental bittersweet along the side of the fields and stone walls I’ll mow it back.

Propane Torch: Backpack-mounted propane torches can be used for invasive plant control.  This method uses targeted fire to heat the base of a plant, killing it.  Some plants with developed roots may re-sprout after this treatment. Safety training is needed before using this method.

Herbicides: Herbicides are pesticides used for vegetation management. Herbicides can be a valuable tool in controlling invasive species, but they must be used with caution. Always read the entire herbicide label and apply herbicides according to label directions. Wear the personal protective equipment specified on the product label and heed any and all environmental restrictions stated on the label. Most herbicide products, especially those marketed to homeowners and small property owners, are classified as “General Use” pesticides. Only licensed pesticide applicators are allowed to purchase or apply “Restricted Use” pesticides.

I use herbicides as infrequently as possible but do keep some handy to control poison ivy. For Japanese barberry, winged euonymus, and thicker vines of oriental bittersweet (too large for hand pulling) I will use the “cut and paint” method in late summer or early fall. I cut the plant and paint or spray the herbicide from a handheld spray bottle directly on the lower cut surface of the stem. I use a strong solution (usually 50/50 water and herbicide and color the liquid with green food coloring to better see where I have applied the herbicide.

Grazing: Grazing means using animals to eat plants. My guess is that goats are the preferred animal for grazing on large swaths of oriental bittersweet. Our horses don’t seem interested in it at all.

If you’re looking for more information on the various (and too many) invasive plants in our region, the challenges they pose and methods of controlling them, I suggest you check out the Connecticut Invasive Plant Working Group at UConn and the website listed above. This group has been around for 20 years and meets several times a year to collaborate and share information. They also hold a biennial invasive plant symposia, with the next one scheduled for October 11^th at UConn.

The Last Green Valley National Heritage Corridor is a region rich in diverse natural resources and habitats. The invasive plant species that we encounter do not diminish the scenic and natural beauty, but serve a challenge to each of us to learn about them, and work together to help control them as best we can.

Bill Reid is the Chief Ranger of The Last Green Valley National Heritage Corridor and has lived in the region for more than 30 years. He can be reached at bill@tlgv.org.

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