Extension Master GardenerSM Volunteers of Buncombe County

Invasive Plants

Non-Native Invasive Plants: Chinese and Japanese Wisteria

Those looping vines of purple-lilac flowers that looked so attractive this spring? Probably non-native wisteria—and proof that you cannot always judge plants by their showy flowers! These vines are extremely invasive, infesting roadsides, forest edges, and rights-of-way. They grow up almost anything in their path—limited only by the height of whatever they climb, with stems reaching up to 15 inches in diameter! They can shade out tree leaves, decreasing photosynthesis, and eventually killing the tree.

Chinese Wisteria (Wisteria sinensis)

Wisteria identification
There are two Asian wisterias that have invaded most of the east coast and all of the southeastern United States: Japanese (Wisteria floribunda), which has lighter bark and twines counterclockwise around its host, and Chinese wisteria (W. sinensis) with dark gray bark that twines clockwise.

Management

Mechanical
For small wisteria infestations, remove entire plants, along with their roots and runners. Any root pieces left in the soil can re-sprout to produce new plants!

For more extensive infestations, cut climbing or trailing vines as close to the ground as possible. Although this may be labor intensive, it is a feasible control in areas where you cannot use herbicides. Cut vines back early in the season, and then every few weeks until the fall. This will stop growth of existing vines and prevent seed production. Remove wisteria vines from the bases of trees and shrubs to prevent girdling as the trees and shrubs grow.

Dispose of fruit, roots, and other plant parts in bags—not in the compost—to prevent re-infestation.

Chemical
The best time to apply an herbicide is in the spring and summer when wisteria is actively growing. Be sure to allow adequate time for the plant to regrow from the winter to ensure movement of the herbicide back into the underground portion.

Foliar application of a 2% (2.5 Ounces (oz) or 5 Tablespoons (Tbsp) per gallon of water) concentration of triclopyr with a 0.5% (0.5 oz or 1.25 Tbsp per gallon of water) nonionic surfactant is an effective control if you wish to use an herbicide. NOTE: If wisteria vines are growing up into trees or other desirable plants, you must pull the vines down prior to application of chemicals to minimize damage to the desirable vegetation. Do not cut the vines at ground level because the herbicide must move into the root system to provide better control!

If you must cut the vines at ground level, you can control the plants using the cut stump treatment method. Cut stems as close to the ground as possible and immediately apply a 25% (32 oz or 4 cups per gallon of water) solution of triclopyr to the stem. Wear disposable plastic gloves and se a disposable paint brush to apply the herbicide in order to ensure adequate coverage of the cut stem and minimize drift to desirable vegetation.

Native alternatives for Chinese and Japanese Wisteria
American Wisteria (Wisteria frutescens), native from Virginia to Missouri and south to Florida and Texas, is a clockwise twining deciduous woody vine that grows to 40 feet or more. It has fragrant, pea-like, lilac-purple flowers in drooping 6-inch long racemes that bloom in April-May after the leaves emerge but before they fully develop. This is an excellent vine for freestanding arbors, pergolas, posts, trellises, fences or terrace walls, but do NOT allow it to grow up desirable trees and shrubs!
Other native plant alternatives:
Hummingbird favorites:
• Coral honeysuckle (Lonicera sempervirens)

Coral Honeysuckle (Lonicera sempervirens)

• Crossvine (Bignonia capreolata)

Crossvine (Bignonia capreolata)

• Trumpet creeper (Campsis radicans)—this one can sucker and holds on with adhesive disks that can damage siding, so plant where it can spread away from your house!

Trumpet Creeper (Campsis radicans)

Butterfly host:
• Dutchman’s pipe (Aristolochia macrophylla)—Host plant for pipevine swallowtail butterflies

Dutchman’s Pipe (Aristolochia macrophylla)

Article by Bob Wardwell, Extension Master GardenerSM Volunteer
For more information:

Wisteria sinensis, Chinese Wisteria:
https://articles.extension.org/pages/62675/wisteria-sinensis-chinese-wisteria

Postemergence, Non-Selective Herbicides for Landscapes and Nurseries
https://content.ces.ncsu.edu/postemergence-non-selective-herbicides-for-landscapes-and-nurseries

As the vine twines:
http://www.namethatplant.net/article_asthevinetwines.shtml

Native vines for butterflies:
https://www.wildlifehc.org/10-native-vines-to-attract-butterflies/

 

Plant Bullies, Part II

So you’ve identified a garden bully, invasive plants. A quick review of your options for dealing with them starts with breaking the reproductive cycle so they do not spread. Don’t let them go to seed, particularly if they’re annuals. Or use a pre-emergent treatment so the seeds don’t germinate.

You can exhaust them by continued weeding, mowing, flaming or maybe grazing goats.Goats

And in the last resort category we have something that those folks back in ’96 lacked – herbicides, chemicals developed to take advantage of the plant’s weakness. Our garden centers have shelf after shelf of bagged and bottled herbicides, and it can be overwhelming when there are several brands with similar claims in big letters on the label. It’s the fine print and the instructions that you need to read, before you buy and then again before you mix and apply. For example, don’t buy a weed-preventer to kill existing weeds. And don’t expect an herbicide to make a distinction between a desirable plant and a weed. Dicamba will kill the roots of any plant, including desirable shrubs and 2,4-D will kill broad leaf weeds but not harm grass, which is why we use it on dandelions in the lawn grass but if it drifts onto a bed of pansies – bad news!

Read the label! Will a pint of diluted, ready-to-use product be all you need or would a gallon of the active ingredient be a much better buy? Maybe you could share with a neighbor. Or the whole neighborhood could attack kudzu at the same time.

How will you apply the herbicide? Do you need to mix with water and spray the leaves? Or is it to be applied at full strength to the freshly-cut woody stump? Is this product less effective at certain temperatures or particular weather conditions?

And if you have questions as to how to attack a particular weed, call the Extension Helpline 828-255-5522.

Written by Extension Master Gardener Volunteer Glenn Palmer.

Plant Bullies, Part I

Back in ’96, 1896 that is, the USDA was explaining to farmers* that “A large proportion of the plants growing along roadsides, on waste ground or older cultivated parts of this country are migratory weeds. They’re not native to where they are now found but have come from other countries or other places in this country.” USDA could use those same words to describe our situation today. Now we call them “invasives” but they move around by the same means as in 1896.

When you think of it, plants have to be able to move or spread to make room for their offspring or find more habitable ground. That USDA Yearbook* went on to describe how plants do move about, starting with the natural methods such as runners. Others throw their seeds as the pod matures and dries. Some seeds such as dandelions or water walnuts are carried further by the wind. Some move by other clever means.Artificial methods of 1896 seed locomotion included one we don’t worry too much about these days – when “cheaper grades of imported crockery are packed in cheap hay or straw”. Or mixed with commercial seeds? The Yearbook had drawings of different seeds so farmers could identify some common “good” vs bad.

The need to clean farm machinery between work in different fields was mentioned. Hmmm, have you ever borrowed a neighbor’s mower? Or rented a tiller? They often come with seeds attached.

Even back in 1896 there were “weeds introduced as useful or ornamental plants…seed of oxeye daisy is said to have been brought to Rhode Island and planted to obtain horse’s feed.” And so on…

The point is that now is the season to keep an eye out for newcomers on your homestead. Look for plants that seem to have spread rapidly, plants that weren’t there last year, or perhaps plants that you cannot identify. Get them while they’re small and easy to control just in case they might be bullies.

If you do have a questionable plant, bring it in for identification. Remember that Extension has moved. We’re now at 49 Mt. Carmel Road in Erwin Hills. The phone number didn’t change: 828-255-5522.

*From the Yearbook of the United States Department of Agriculture 1896

Next week part II will review options for dealing with those bullies.

Written by Glenn Palmer, Extension Master Gardener Volunteer.

Contact Us

Buncombe County Extension Office
49 Mount Carmel Road
Asheville, NC 28806
Helpline 828-255-5522

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