Extension Master GardenerSM Volunteers of Buncombe County

Invasive Plants

Non-native Invasive Plants: Nandina domestica (Heavenly Bamboo)

Nandina domestica, Cathy Dewitt, (Wake County, NC) CC BY 4.0

As the long-lasting bright red berries form and the dark green foliage turns burgundy in autumn, heavenly bamboo (Nandina domestica) shows off why it is a popular choice for a fast-growing shrub with four-season interest. The fact that these broadleaf evergreens thrive under many different soil, temperature, and light conditions, are deer resistant, and have few insect or disease problems is what makes them problematic as exotic invasive plants!

Nandina invading natural areas. Image by Chris Evans, University of Illinois, Bugwood.org

What’s the problem?
Landscape disturbance.
Although this Asian native was introduced to the United States in the early 1800s as a desirable ornamental shrub Nandina domestica spreads so quickly from both rhizomes and seeds that it is now invading much of the southeast. Dense clusters of Nandina domestica displace native vegetation and decrease light levels in forested areas.
Bird and mammal impact.
Birds and mammals disperse the hundreds of seeds these shrubs can produce to both developed and natural areas. Nandina berries contain cyanide that can reach toxic levels. Cedar waxwings consuming large quantities of the berries have died from cyanide poisoning. Domestic and grazing animals can also become ill from eating the berries.

Managing Nandina domestica in your garden to prevent its spread
Mechanical
You can hand pull new seedlings, and dig out shrubs, but you must remove all root fragments, so the plants won’t regenerate. Established plant removal is often difficult due to the shrubs’ extensive root systems. If you haven’t yet succeeded in removing mature plants, cut off the white flowers when they have faded before the berries form. If berries are already present, remove and dispose of them in the trash, not your compost pile.
Chemical
If having difficulty removing large shrubs, you can turn to herbicides, which may require several applications. The North Carolina Agricultural Chemicals Manual recommendations for woody plant control include herbicides containing glyphosate and triclopyr. For most effective control of Nandina domestica, the USDA Forest Service Southern Research Station recommends foliar wetting with glyphosate mixed with a surfactant only from August to October. If you prefer to cut back the shrubs, use glyphosate or triclopyr mixed with a surfactant painted on freshly cut stumps shortly after making the cuts. To prevent run-off, make these stem cuts level and close to the ground. Always follow the label instructions for determining the application rate (percent solution) for either method.

Replacing Nandina domestica in your landscape
There are shorter, more compact varieties of Nandina domestica that produce few, if any, berries. Examples include ‘Fire Power’ 2 to 2 1⁄2 feet, ‘Gulfstream’ 3 to 3 1⁄2 feet, and ‘Obsession’ 3 to 4 feet tall and wide, respectively. Obviously, these selections won’t fill the same space and purpose as the original shrubs and if they do produce berries, the berries must be removed to prevent seeding. So, what are your alternatives? Many native shrubs can provide attractive substitutes for Nandina domestica. Recommendations for desirable, wildlife friendly shrubs include:

Winterberry (Ilex verticillata)
  • Winterberry (Ilex verticillata)
  • Dwarf Fothergilla (Fothergilla gardenii)
  • Smooth hydrangea (Hydrangea arborescens)
  • St. John’s Wort (Hypericum frondosum)
  • Inkberry (Ilex glabra)
  • Eastern red cedar (Juniperus virginiana)
  • Arrowwood viburnum (Viburnum dentatum)

Article written by Carol Anne Reynolds, Extension Master GardenerSM Intern.

For more information:
https://plants.ces.ncsu.edu/plants/nandina-domestica/
Invasiveness:
http://nc-ipc.weebly.com/nandina-domestica.html
Toxicity:
https://vet.uga.edu/toxicity-due-to-nandina-domestica-in-cedar-waxwings-bombycilla-cedroru/
Native alternatives:
https://plants.ces.ncsu.edu/plants/ilex-verticillata/
https://plants.ces.ncsu.edu/plants/fothergilla-gardenii/
https://plants.ces.ncsu.edu/plants/hydrangea-arborescens/
https://plants.ces.ncsu.edu/plants/hypericum-frondosum/
https://plants.ces.ncsu.edu/plants/ilex-glabra/
https://plants.ces.ncsu.edu/plants/juniperus-virginiana/
https://plants.ces.ncsu.edu/plants/viburnum-dentatum/
Chemical control:
North Carolina Agricultural Chemicals Manual:
https://content.ces.ncsu.edu/north-carolina-agricultural-chemicals-manual
A Management Guide for Invasive Plants in Southern Forests:
https://www.srs.fs.usda.gov/pubs/gtr/gtr_srs131.pdf

 

 

 

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

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

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