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The fruit of Oriental Bittersweet

An oriental bittersweet vine has engulfed a black locust tree

An oriental bittersweet vine has engulfed a black locust tree

The other day as I drove down our road on my way to work, a bright patch of yellow and red caught my eye. I looked over and saw a colorful bittersweet vine draped over a dead black locust tree at the edge of the road. Since I had my camera with me, I stopped to take some pictures.

The berries of bittersweet are quite beautiful and sections of these berry laden vines are often used in natural fall arrangements.

But Beware!

There are two types of bittersweet vines that can be found over much of the eastern half of the United States; the good guys, American Bittersweet (Celastrus scandens) and the alien invaders, Oriental Bittersweet (Celastrus orbiculatus).

Bittersweet vines are a colorful addition to festive fall arrangements

Bittersweet vines are a colorful addition to festive fall arrangements

Unfortunately, the bittersweet that is growing on our property is oriental bittersweet and by all accounts, I should go out with Roundup and kill it off – the sooner the better. How sad because it is such a colorful vine and would be great for fall decorating. I guess I could still harvest some nice pieces of the vine before we annihilate it!

Oriental bittersweet is a deciduous vine that is native to Asia. It was introduced to the United States in the 1860’s as an ornamental plant. I can understand why it was considered desirable because the fall berries are very colorful and extremely plentiful on the vine.

On the other side of the road, oriental bittersweet climbs over a locust and into the cedars.

On the other side of the road, oriental bittersweet climbs over a locust
and into the nearby cedars.

According to the Plant Conservation Alliance, though, oriental bittersweet has escaped from cultivation and become an “ecological threat” to our native plants because the vigorous vines quickly grow up and over trees and shrubs. Eventually they kill the trees by either girdling them with their thick constricting vines, shading them out with their dense foliage, or uprooting them with their excessive weight (especially after a heavy snow). In addition, oriental bittersweet is successfully outcompeting our native species, American bittersweet, and replacing it in the wild. Oriental bittersweet has been listed as an invasive species in at least 21 states.

One of the reasons that it spreads so easily is that it reproduces readily from seed – and it produces a lot of seed. In addition to germinating from fruit that drops to the ground, the seeds are also dispersed by birds that eagerly gobble up the berries and deposit the seed over a wide area. The plants are pretty adaptable to different growing conditions so these “deposited” seeds often germinate where they drop.

Bright yellow capsules split open in the fall revealing the colorful red fruit

Bright yellow capsules split open in the fall revealing the colorful red fruit

Both American bittersweet and oriental bittersweet are dioecious which means they have separate male and female plants, like hollies. Berries are only produced on the female plants and only if a male plant is in the area to pollinate the female flowers.
A relatively new cultivar of American bittersweet, Celastrus scandens ‘Bailumn’ (Bittersweet Autumn Revolution), produces flowers with both male and female parts (perfect flowers) so only one plant is needed to have beautiful berries in the fall. This is a great variety to plant in the landscape – just don’t plant it where it can climb on your trees or shrubs because, like the oriental bittersweet, it can damage and even kill them if it grows over them.

Oriental bittersweet easily overtakes trees and other plants in its path

Oriental bittersweet easily overtakes trees and other plants in its path

So how do you get rid of this extremely invasive alien plant? First make sure it is not an American bittersweet – these we want to save. If it is indeed oriental bittersweet, you can try digging it out but sometimes this is difficult. If it isn’t practical to remove them manually, you can control them by applying a product that contains glyphosate (such as Roundup) or a product that contains triclopyr (such as Bayer Advanced Brush Killer Plus). Be sure to read and follow the label directions when applying either of these chemicals. More information about identifying and controlling oriental bittersweet can be found on the Plant Conservation Alliance website.

I suspect that the oriental bittersweet vine along our road had something to do with the demise of the black locust tree it was growing on but I’m not particularly sad because I’m not especially fond of black locust. However, I guess in the name of ecological preservation, we should go out this weekend and destroy this unwelcome alien.

But the fruit is so pretty, I wish there was some other way …

Until next time – Happy Gardening!

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