Extension Master GardenerSM Volunteers of Buncombe County

Invasive Plants

Non-Native Invasive Plants: Japanese Spirea

Japanese Spirea

What is Japanese spirea?
Gardeners imported Japanese spirea (Spiraea japonica) to the United States in 1870 for use in Victorian-era landscapes. The easy-to-grow shrubs with the compact habit and pink flowers remained a favorite. Now Japanese spirea is one of many Asian shrubs threatening the ecosystems of our native southern forests.

Why is it a problem?
Japanese spirea has small seeds that wash away and rapidly take over disturbed areas; they are especially a problem when they reach stream banks. Seeds may also arrive in fill dirt used in home construction.

Once established, Japanese spirea forms dense stands that outcompete the native forest flora. Seeds from Japanese spirea can last for years in the soil, making the spread difficult to control. Note that although Japanese spirea is not yet on North Carolina’s statewide list of invasive plant species, it is specifically noted as an invasive plant in Buncombe County and the Great Smoky Mountains National Park.

Some cultivars of the invasive Japanese spirea have golden leaves like this ‘Goldflame’ spirea

How Can I Help?
Don’t plant Japanese spirea! Consider using native plants in your landscape. Some alternatives are:
• The native spireas, white meadowsweet (Spiraea alba),

The native meadowsweet has white flowers.

• sweet pepperbush (Clethra alnifolia),
• silky dogwood (Cornus amomum),
• leatherleaf (Dirca palustris),
• Virginia sweetspire (Itea virginica),
• ninebark (Physocarpus opulifolius).

This native clethra has pink flowers.

Consider removing existing plants.
If you can’t easily dig up your planting, cutting back and repeated mowing can help eliminate unwanted shrubs. Be sure to keep cutting back to prevent seed production!
For large infestations, herbicides containing triclopyr or glyphosate are effective. Be careful to follow label directions!

Article by Barbara Hayes, Extension Master GardenerSM Volunteer

For more information:
Weed of the Week:https://www.invasive.org/weedcd/pdfs/wow/japanese-spiraea.pdf

Distribution of Japanese spirea:https://www.invasiveplantatlas.org/subject.html?sub=3076

Invasive exotic plants in the Great Smoky Mountains National Park:https://www.nps.gov/grsm/learn/nature/non-natives.htm

Non-Native Invasive Plants: Bamboo—The Plant We All Love to Hate!

A visitor to the Extension Master Gardener office told me he had a plant to identify that was too big to bring inside—that got my interest. In the back of his truck he had a grass-like plant over 10 feet tall with hollow stems!

 Bamboo or river cane?

I was looking at either a running type of bamboo (Phyllostachys spp.) or another form of bamboo: river cane (Arundinaria spp.). The difference between the two? One is an extremely aggressive invasive native and the other is a native.

 Phyllostachys aurea is a bamboo species of the ‘running bamboo’ type. It is commonly known by the names fishpole bamboo and golden bamboo.  This is the species most widely seen in the landscape. A related species is Phyllostachys nigra—black bamboo—is also widely cultivated and invasive! They both form dense—almost impenetrable—thickets that crowd out all other plants.

Invasive Bamboo

Arundinaria is the only bamboo native to North America, found in the south-central and southeastern United States. It is tree-like, growing to heights up to 26 ft. It has distinctive fan-like cluster of leaves at the top of new stems called a top knot. Arundinaria gigantea, commonly known as river cane, is a woody plant native to North Carolina.  River cane communities occur on floodplains, bogs, along streams and rivers and in riparian woods.

River Cane

It became obvious to me that my visitor just wanted it gone from his yard!

Dr. Joseph C. Neal, Department of Horticultural Science, at NC State University, discusses three techniques for dealing with bamboo in the publication “Controlling Bamboo in Landscape Plantings.”

Removal

To eliminate a planting completely requires physically removing as much of the top growth and root mass as possible—this will require power equipment for large infestations! Bamboo will regenerate from any small rhizomes left behind so long-term follow-up will typically require the use of herbicides or planting the area in lawn:

  • Chemical control involves spraying with a post-emergent, non-selective herbicide such as glyphosate and may require repeated spraying whenever new growth occurs.
  • Convert to lawn avoids the use of herbicides and relies on the fact that bamboo will not tolerate frequent mowing. This works only if you mow the entire area! If you don’t eliminate the entire stand, new shoots will keep moving in from the remaining plants.

Containment

  • If you want to contain a bamboo planting, you can install a barrier— concrete, metal, plastic, or pressure-treated wood—installed at least 18 inches deep that slants outward and rises at least a couple of inches above the ground. Because barriers only deflect rhizomes rather than prevents them from growing, you will need to inspect the barrier at least yearly to remove any new rhizomes.

Regardless of which method of control you choose, eradicating a bamboo infestation requires intensive effort over several years.  Of course, the best way to prevent bamboo from becoming a weed is to avoid planting the invasive, spreading-type bamboos in the first place—and ask your neighbors to avoid it, too!

 Article by Bob Wardwell, Extension Master GardenerSM Volunteer

Controlling bamboo in landscape plantings:

https://content.ces.ncsu.edu/controlling-bamboo-in-landscape-plantings

Identifying Native Bamboo: www.namethatplant.net/article_nativebamboo.shtml

More about river cane:

http://www.indefenseofplants.com/blog/2017/6/26/north-americas-native-bamboos

Non-Native Invasive Plants: Oriental Bittersweet (Celastrus orbiculatus)

If you knew how awful it is, you would have nothing to do with oriental bittersweet! It is an aggressive, woody, deciduous, perennial vine capable of girdling stems and trunks of shrubs and trees, damaging their bark and underlying tissue. Despite its weedy behavior, oriental bittersweet is still sold and planted as an ornamental vine and should be avoided.

Oriental bittersweet vine chokes tree_photo by G. Merrill
Oriental bittersweet vine

Identification:

  • Leaves: Finely toothed, round glossy leaves are arranged alternately on the vine. They range from 2 to 5 inches long and 1.5 to 2 inches wide.

    Oriental bittersweet (Celastrus orbiculatus)_Leonara Ellie Enking_CC BY-SA 2.0_Flickr
    Oriental bittersweet foliage
  • Flowers: Clusters of 2 to 7 blossoms where the leaf attaches to the stem (leaf axil). Each flower has 5 petals and 5 sepals.
  • Fruit: Green-to-yellow round fruits ripen in the fall. Upon ripening, the fruits split open revealing three red-orange, fleshy berries that remain on the vine through the winter. The many birds and small mammals that feed on the berries distribute seed far and wide. A single plant can produce almost 400 fruits!

    Oriental Bittersweet_berries_Katja Schulz_CC BY 2.0_Flickr
    Oriental bittersweet Fruit
  • Distribution: Oriental bittersweet’s distribution ranges from central Maine south to North Carolina and west to Illinois;
  • Ecology: It can grow in woodlands, fields, hedgerows, coastal areas, and salt marsh edges. It tolerates shade but prefers full sun.

Management Options:

  • Mechanical control: Pull light infestations by hand—before fruiting, if possible. If fruits are present, bag the vines to make sure the seeds do not contaminate the site. Cutting the vines at the base early in the season will prevent flowering and fruiting, but you must remove all of the roots so the bittersweet will not re-sprout. Frequent mowing will also exclude oriental bittersweet, but infrequent mowing—two to three times a year—can stimulate root suckering.
  • Chemical control: You can successfully manage heavy infestations of non-native bittersweet with herbicides containing the active ingredient Triclopyr. The chemical is most effective applied immediately to the cut stem surface of cut or mowed vines. Apply herbicides prior to the emergence of native plants or after the last killing frost to help avoid herbicide contact with desirable plants. As with any herbicide, carefully follow the label guidelines when handling and applying.

American bittersweet (Celastrus scandens) is native to the eastern United States and is easily confused with oriental bittersweet. Leaf shape is highly variable and not a good characteristic for identifying American vs. Oriental bittersweet. Watch for flowers and fruits to distinguish the two:

  • American bittersweet flowers and fruits are only found at the ends of stems, Oriental bittersweet flowers and fruits are found all along the stem at leaf axils.
  • American bittersweet has orange capsules around red fruits, Oriental bittersweet has yellow capsules around red fruits.

A HOLIDAY CAUTION: Do NOT use oriental bittersweet in outdoor decorations! If you have any decorations containing oriental bittersweet fruits, be sure to bag them and discard—Do not compost!

Article by Bob Wardwell, Extension Master GardenerSM Volunteer

For More Information:

 

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

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