It appears quite pretty when you notice it growing along the roads of Madison County. “Pretty” is certainly what the collector who brought it from Japan nearly 200 years ago must have thought. And growing probably isn’t the appropriate word…. perhaps taking over is a better description. This large shrub with drooping tassels of white flowers set off by purple-brown stems and shovel-shaped green leaves might seem the perfect plant to fill in the garden at the end of summer when many other flowers have gone to seed. But beware of first impressions!

Japanese Knotweed has been described as a thug, relentless and overwhelmingly aggressive and probably just as often by words not fit for print. It forms dense, bamboo-like clumps up to seven feet high and spreads rapidly, mostly through creeping underground stems (rhizomes) that can grow more than three feet a month. It is so vigorous it can cause pavement to heave and crack, after which it sends up new shoots through the cracks it has made. It can damage buildings in the same manner. A tiny piece of rhizome from Japanese Knotweed can produce a new plant in ten days and a tiny piece of rhizome can remain dormant in the soil for twenty years before waking up and giving birth to a mighty horde of new invaders.

If you have Japanese Knotweed get rid of it! Eradication requires steely determination, so call the Extension Office for advice. And if you love tassels of white flowers at the end of summer, raise your eyes to the native sourwood trees that are blooming at this time of year. They are not invasive and, by the beginning of fall, will set off their white flowers with bright red leaves.

By the 1990’s, breeders had developed cultivars of Callery Pear that did cross pollinate. These were sold and planted with the same enthusiasm as the 1960 variety. The fruits (each containing up to ten seeds) of these new, fertile trees were eaten by birds and dispersed into nearby fields, parks and other open and disturbed areas, creating an invasive wild population of hybrid Callery Pears.

These new hybrids began to unbalance native plant communities. Their tendency to split and break resulted in an increase in power outages and damage to cars and homes. Because of these problems, many nurseries now refuse to sell them and some states are starting campaigns to stop their spread. If you already have Bradford Pears don’t cut them down. But if they break or die you might consider different trees as replacements. If you are longing for an early blooming tree with white flowers, consider planting Serviceberry or our native Dogwood, which not only has beautiful flowers but an abundance of red berries in the fall.

If you purchase a bittersweet vine from a nursery be sure it is American bittersweet, which is native to North America east of the Rocky Mountains and less invasive than its Asian cousin.

The easiest way to tell the difference between Oriental and American bittersweet is that American has orange berries located at the end of each stem. Oriental bittersweet has its berries in leaf axils along the length of the stem and the seed capsules are yellow. If you do decide to make a wreath with Oriental bittersweet, when the season has ended discard it with care. Be sure to place it in a plastic bag and put it in the trash. Don’t throw it into the woods or on a compost pile as the berries can germinate and produce new, invasive vines.

Princess tree was introduced into the U.S. as an ornamental and landscape tree around 1840. It was imported to Europe in the 1830’s by the Dutch East India Company and brought to North America a few years later. This tree has since become naturalized in the eastern U.S. Historical records describe its medicinal, ornamental, and timber uses as early as the third century B.C. It was cultivated centuries ago in Japan where its wood is still highly valued.

Princess tree can reproduce from seed or from root sprouts which can grow more than 15 feet in a single season. The root branches are shallow and horizontal without a strong taproot. Seed-forming pollen is fully developed before the onset of winter and the insect-pollinated flowers open in spring. A single tree is capable of producing an estimated twenty million seeds that are easily transported long distances by wind and water and may germinate shortly after reaching suitable soil. Seedlings grow quickly and flower in 8-10 years. Mature trees are structurally unsound and rarely live more than 70 years. Princess tree can be controlled using a variety of mechanical and chemical controls. Hand pulling may be effective for young seedlings. Plants should be pulled as soon as they are large enough to grasp. Seedlings are best pulled after a rain when the soil is loose. The entire root must be removed since broken fragments may resprout. Trees can be cut at ground level with power or manual saws. Cutting is most effective when trees have begun to flower to prevent seed production. Because Princess tree spreads by suckering, resprouts are common after cutting. Cutting should be considered an initial control measure that will require either repeated cutting of resprouts or an herbicidal treatment.

Large trees should be cut down with a chainsaw and the outer two inches of cut surface of stump treated with undiluted glyphosate concentrate (53.8% is preferable). Large saplings can be killed in a similar fashion, taking care to treat the entire cut surface. If seed capsules are present on cut limbs,, they should be collected, bagged and disposed of in heavy garbage bag so they do not spread.

Japanese honeysuckle was brought here from Asia and has spread steadily. It is is usually seen on the edges of woods, streams, or roads. It also lives in fields and gardens. Japanese honeysuckle has three-inch leaves which are green and oval-shaped. They are opposite, which means two leaves grow as a pair from the same spot on the stem, but on opposite sides. Birds that consume the fruits and disperse the seed spread Japanese honeysuckle. However, this species is also capable of reproducing vegetatively by underground rhizomes, and aboveground runners. It also has the ability to develop a rather large seed bank after becoming established and seeds germinate after soil disturbance. Wide habitat adaptability, wide seed dispersal, rapid growth rate, extended growing season, and lack of natural enemies make Lonicera japonica a strong competitor against native species.

Management:

Manual: Hand-pulling, grubbing with a hoe or a shovel, and removal of trailing vines is practical for small infestations. Remove and destroy all plant material after cutting to prevent rooting and reinfestation. Periodic mowing can slow vegetative spread but may cause resprouting and increase stem density. Aggressive mechanical tillage is also effective, but may not be an option in many areas. However, soil disturbance may stimulate seed germination from the seed bank.

Chemical: Timing of application is critical to effective Japanese honeysuckle control. Many herbicide treatments reduce foliage but leave buds and roots undamaged that can produce new growth. A foliar application of 1.5 to 3% glyphosate or 3 to 5% triclopyr shortly after the first frost appears to be the most effective treatment.

Biological: Lonicera japonica has few natural enemies in North America. There are no known biological agents for Japanese honeysuckle. Deer may forage on the plant, but cause limited damage.

Nandina is considered invasive in North Carolina, Tennessee, Georgia and Florida. It has been placed on the Florida Exotic Pest Plant Council’s invasive list as a Category I species, the highest listing. Nandina has been observed invading open fields and wooded areas throughout North Carolinal. In general, the purchase or continued cultivation of these plants in the southeastern US is highly discouraged. Sacred bamboo foliage and fruit are poisonous to some animals. The foliage contains cyanogenic glycosides, which are poisonous to many animals. Even small amounts of foliage are hazardous to cattle and animals may become comatose 5 to 10 minutes after the first signs of poisoning appear. Sacred bamboo berries are toxic to dogs and cats and mildly toxic to humans.

Management: The first step in preventative control of nandina is to limit planting and remove existing plants within the landscape. If possible, removal should occur before seeds are produced. Since seeds remain on the plant for several months, care must be exercised to prevent seed spread and dispersal during the removal process. Chemical control can be accomplished by thoroughly wet all leaves with glyphosate herbicide as a 1-percent solution in water (4 ounces per 3-gallon mix) with a surfactant (August to October). Currently there are no known biological controls for heavenly bamboo.

Flowers are clustered, fragrant, with a four-lobed pale yellowish-white bloom along the stem. Fruit, which is called a drupe, is a round and 1/4 to 1/3 inches long, silvery-scaled yellow ripening to red dotted with silver or brown coloring. Ripe fruit is juicy and edible. It is small but abundantly produced, tart-tasting, and has a chewable seed. These fruits have been shown to have about 10 times the amount of the antioxidant lycopene than tomatoes.

Autumn olive and Russian olive spread by seeds disseminated throughout the landscape by birds and other wildlife that eat them. The shrubs grow rapidly and out-compete native vegetation. Olives begin to produce fruit as early as 3 years of age, and have the ability to thrive in poor soil. It often invades riparian habitats where overstory cottonwood trees have died. Olive seedlings re-sprout vigorously after cutting or burning.

Hand pulling seedlings and sprouts is effective in the early spring when the ground is moist and the entire plant and roots can be removed. Other forms of control such as mowing and burning without the application of a herbicide usually contribute to a larger number of root sprouts. Systemic herbicides, such as Roundup (glyphosate), can be used effectively when applied to cut stumps or used as a foliar spray. There are currently no biological controls for either olive varieties.

Consider these native plants as alternatives: black-haw (Viburnum prunifolium), shadbush (Amelanchier arborea, A. laevis), clammy locust (Robinia viscosa), redbud (Cercis canadensis), New Jersey tea (Ceanothus americanus) and staghorn sumac (Rhus typhina).

The stems can add 20 or more inches per year making them prolific growers. Once you are able to identify privet, you will notice it grows along almost every roadside. Privets persist on abandoned home sites and can readily invade abandoned lots and farmlands where they form impenetrable thickets. They are especially abundant along fencerows, streams, roadsides, and forest margins, and even have the ability to invade forests. Privets were introduced into the United States from Asia for ornamental planting, particularly for hedges. Having escaped from cultivation, they have now spread widely throughout the southeastern United States. The greatest threat is their ability to successfully compete with and displace native vegetation. The plants mature rapidly and are prolific seed producers. They also reproduce vegetatively by means of root suckers. Once established, they are difficult to eradicate because of their high reproductive capacity.

Management: Because privets are so invasive, aggressive management is key. Small shrubs can easily be pulled by hand. The larger ones should be cut near their base and an herbicide like Roundup applied to the cut area. For more information, go to http://plants.usda.gov/plantguide/pdf/pg_lisi.pdf.

Mimosa reproduces both vegetatively and by seeds which have impermeable seed coats that allow them to remain dormant for many years. One study showed that 90% of the seeds were viable after five years, and for another species of mimosa, a third of its seeds germinated after 50 years in open storage. Seeds are mostly dispersed below or around the parent plant, but can be dispersed further by water. Silk trees grow rapidly under good conditions but are short-lived and have weak, brittle wood. If cut or top-killed, trees resprout quickly and sprouts can grow over three feet in a single season.

To manage this tree, cut off at ground level with power or manual saws. Cutting is most effective when trees have begun to flower. This will prevent seed production. Because mimosa spreads by suckering, resprouts are common after treatment. Cutting is the initial control measure. Complete removal will require either an herbicidal control or repeated cutting of resprouts. Systemic herbicides such as glyphosate and triclopyr can kill entire plants because the chemical travels through a plant from the leaves and stems to the actively growing roots, where they prevent further cell growth.

Japanese barberry is native to Asia. It was brought to North America in the late nineteenth century and has been widely planted as an ornamental. It has escaped and naturalized as far north as Nova Scotia, south to NC and west to Montana. The plant regenerates by seed and creeping roots. Birds and rabbits are known to eat the seeds and distribute the species. Branches root freely when they touch the ground, allowing single plants to become quite large. Japanese barberry competes poorly with grasses and may succumb to drought conditions.

Mechanical removal is recommended because it is effective and may cause the least disturbance. Barberry is one of the first plants to leaf out in spring and is therefore easy to distinguish from other shrubs. whole shrubs may be removed with a hoe or weed wrench. Use of thick or sturdy gloves is recommended to provide protection from the spines. Plants can resprout from roots, so remove as much of the roots as possible. Regular mowing can prevent barberry from returning once it has been removed. In areas where mechanical removal is not practical, such as rock piles or outcrops, a glyphosate herbicide can be used. Consult a licensed herbicide applicator before applying herbicides over large areas.

Identification: Chinese Silvergrass is a bunched perennial grass reaching 5 to 10 feet in height. Leaves are alternate, 40 inches long, and pointed. The stem is stout and arching. The silver or pink flowers are branched and drooping, 4 to 15 inches long, and appear from August to November. The yellowish-brown seeds mature from September to January.

Ecology: Chinese Silvergrass invades roadsides, field edges, and disturbed sites. This invasive grass colonizes by wind dispersed seeds. It is highly flammable and may become a fire hazard. Few wildlife species use Chinese Silvergrass.

Plant Control: In the home landscape, Miscanthus clumps can be dug up and bagged in large heavy duty garbage bags so the clumps cannot root elsewhere and the seeds do not spread. If digging is not an option, spray actively growing clumps with a 2% solution of glyphosate and surfactant. Cut off and bag up any seed heads to control spread. Re-treat as needed until clump is dead. Monitor for seedlings and dig up when found.

http://www.ncsu.edu/goingnative/howto/mapping/invexse/chineses.html