Invasive Species

RiverLink works to improve water quality, healthy ecosystems and riparian zones enable nature to do her work best. In conjunction with many of our projects, within our local target watersheds, and conservation easements we work with volunteers and landowners to remove invasive species to allow for a more diverse and healthy ecosystems. Check out our calendar of events for volunteer opportunities removing invasive species, or contact our Watershed Resources Manager at waterresources@riverlink.org.

Successful weed control depends upon significant reduction of a weed’s ability to reproduce. For this reason, it is important to understand the life cycle of your target weed. The following guide provides basic information on the characteristics of ten common riparian weeds in Western North Carolina, and gives suggestions for methods of control.

The guide includes:

  • Chinese privet (Ligustrum sinense)
  • English ivy (Hedera helix)
  • Japanese honeysuckle (Lonicera japonica)
  • Japanese knotweed (Fallopia japonica)
  • Kudzu (Pueraria montana)
  • Multiflora rose (Rosa multiflora)
  • Nepalese browntop (Microstegium vimineum)
  • Oriental bittersweet (Celastrus orbiculatus)
  • Princess tree (Paulownia tomentosa)
  • Tree of heaven (Ailanthus altissima)

Download Weed Guide(PDF)

Chinese Privet
Species Characteristics
Scientific Name: Ligustrum sinense
Growth Form: Perennial, semi-evergreen shrub
Reproduction: Vegetative (rhizomatous), seed
Season of Flowering: Late spring

Management Information
This shade tolerant perennial produces toxic fruit that is widely spread by birds and mammals. It reproduces via seed as well as vegetatively through root sprout. The root system is shallow so for small populations, hand removal is effective. In order to weaken the plant most efficiently and to eliminate seed production, pull entire plants in late spring when they are in flower but before they have begun to fruit. When handling the plant during flowering, a mask may be useful as the flower fragrance can cause sinus irritation. When pulling, be sure to remove as much of the root system as possible to avoid re-sprout, and clip any re-sprout that does occur. Browsing animals often consume the re-growth of Chinese privet and so use of goats to control sprouting is a possibility. Repeated mowing is another option. Mow plants as close to the ground as possible then let plants grow to about two feet and then mow again. Repeat until root system is exhausted. If you choose to use herbicide to control Chinese privet, combining it with hand pulling or moving will be most effective. Pull or mow the plants to the ground in late spring during flowering. When the re-growth has reached about two feet, and with the plant still actively growing, apply a systemic herbicide. For increased effectiveness, repeat your treatments as many times as possible within a growing season.

English Ivy
Species Characteristics
Scientific Name: Hedera helix
Growth Form: Perennial, evergreen vine
Reproduction: Vegetative (stoloniferous), less often by seed
Season of Flowering: Late summer

Management Information
English ivy is the most common of a suite of invasive ivies found in the southern United States. This evergreen, perennial vine forms monocultures as ground cover and is also a vigorous climber. Because English ivy requires especially sunny conditions to flower, it does not often fruit. Fruits that are produced are poisonous to humans and can be spread long distances by birds. To avoid fruiting, remove the vines from trees where they are reaching higher light levels. To remove from trees, cut the vines away from the base of the host tree. It’s best to cut each vine at two places as to leave a gap so that the vines do not have a chance to heal together. Avoid pulling vines loose from the bark as this can open the host to infection. The most common mode of English ivy reproduction is via stolons; the plants root at nodes in the vine wherever they come into contact with soil. Ground infestations can be controlled by hand pulling and herbicide application. Herbicide application will be most effective in the spring during active growth. For large infestations that require wider herbicide applications which could come into contact with non-target plants, a fall application when other plants have lost their leaves is best. If this avenue is taken, temperatures must be at least 60 °F to ensure growth is occurring at a rate high enough for the herbicide to be effective. Hand pulling can be conducted at any time and is most effective if followed by a systemic herbicide application once the remnants have produced re-growth. Hand pulling may be easiest during the winter when most forest undergrowth has died back making it easy to spot the evergreen English ivy. When hand pulling, be careful not to confuse English ivy with poison ivy. Both plants have hairy stems that climb trees but the evergreen leaves of English ivy are dark green and leathery while poison ivy looses its thin, lighter green leaves in winter, so stay away from leafless hairy vines during winter! To avoid spreading ivy during hand pulling, bag pulled plants immediately or place in a location to dry away from potential contact with soil. As English ivy grows close to the ground, mowing is generally not practical; however, persistent mulching can be effective. The infestation must be completely covered with at least two inches of mulch, for at least two growing seasons. This technique kills the plants by starving them of light. For increased effectiveness, repeat your treatments as many times as possible within a growing season.

Japanese Honeysuckle
Species Characteristics
Scientific Name: Lonicera japonica
Growth Form: Perennial, semi-evergreen vine
Reproduction: Vegetative (stoloniferous and rhizomatous), less often by seed
Season of Flowering: Late spring to early summer

Management Information
Japanese honeysuckle is a common weed in the southeastern United States. This perennial vine climbs by twining around host trees and shrubs and is capable of girdling trees. It is not uncommon for this plant to produce seed but, because the seed tends to be of low viability, Japanese honeysuckle reproduces vegetatively (stem and root sprout) more commonly. Infestations can be controlled by both hand pulling and herbicide application. As might be expected, control is most successful when these methods are used in combination. Herbicide application will be most effective in spring during active growth. Hand pulling can be conducted at any time, but if it is only practical to pull by hand once per year, do it when the plant is in flower. During flowering, hand pulling weakens the root system significantly and at the same time eliminates reproduction. Repeated mowing has a similar effect to pulling. Mow plants during flowering, let plants re-grow then mow again, repeating until root system is exhausted. Application of systemic herbicide to the re-growth after mowing is an effective option. To remove from trees, cut the vines away from the base of the host tree. Avoid pulling vines from the trees especially if they are large. The vines, or the branches that they are attached to, can fall and cause serious injury. Care should be taken when disposing of plant parts. Bagging plants to be taken off-site is recommended as it is difficult to kill roots and stems through drying because of their woody nature.

Japanese Knotweed
Species Characteristics
Scientific Name: Fallopia japonica
Growth Form: Perennial, deciduous sub-shrub
Reproduction: Vegetative (rhizomatous and stoloniferous), seed
Season of Flowering: Summer

Management Information
Japanese knotweed is an aggressive, fast growing, perennial plant that can reach heights of ten feet each season. Successful control of this plant depends on weakening the root system of existing plants and eliminating annual seed production. A combination of physical removal and systemic herbicide application is suggested. Because Japanese knotweed grows particularly quickly, multiple treatments throughout the growing season will be especially effective. Physical control such as hand pulling, mowing, or clipping should be conducted before herbicide application to increase shoot to root ratios and therefore increase plant susceptibility to herbicide. Herbicide should be applied when the plant is actively growing, but before re-sprout grows too high and before seeds are produced. Probably due to high growth rates and large, herbaceous leaves, herbicide applications can be quite effective if implemented properly. As this species readily spreads vegetatively, any invasions adjacent to the target population should also be treated. Care should be taken when disposing of plant parts. The tubular structure of the stem allows even small pieces of Japanese knotweed to float and thus travel readily through waterways colonizing new habitats along the way. To avoid spreading the plant during physical removal, bag plant parts before taking off site or be sure that roots, as well as stems, are thoroughly dried to ensure kill before allowing materials to have contact with soil on site.

Kudzu
Species Characteristics
Scientific Name: Pueraria montana
Growth Form: Perennial, deciduous vine
Reproduction: Vegetative (rhizomatous and stoloniferous), less by seed
Season of Flowering: Late summer

Management Information
This woody, perennial vine is deciduous and extremely fast growing, reaching average growth rates of a foot per day during the growing season. Kudzu is tap-rooted and many vines originate from each root. The plant can also root anywhere its vine comes into contact with soil. To control kudzu, vines should be cut from trees and vines growing along the ground should be pulled and followed to the main tap-root. When the tap-root is located, the root can be killed by cutting off the root crown (the crown is the top part of the root where the vines grow from). Cut the root a few inches below the lowest growing point. Note that if a rooted ground vine is severed from its original tap-root, it will develop a new tap-root and so it is important to remove rooted ground vines and not just the original tap-roots. Treatment should occur before the plant begins to develop seed in late summer. Repeated mowing is another option for control. Treat plants with an initial mow, allow plants to grow to a height appropriate to your mower and then mow again. The goal is to repeat mowing until the root system is exhausted. A systemic herbicide applied to re-growth, either after mowing or hand pulling, will increase control effectiveness. It is generally less effective to control full grown plants (as opposed to re-growth) with herbicide because it is difficult to apply the herbicide adequately over the entire plant due to its large size. In addition to reproducing from root and stem sprout, kudzu also reproduces via seed. Fortunately, many of the seeds produced by kudzu are not viable. Unfortunately, the viable seeds that are produced can remain dormant in the soil for multiple years before sprouting. For this reason, vigilant monitoring for new seedlings is important once the initial infestation has been controlled. Kudzu is a very difficult weed to eradicate but its removal has an extra benefit. Kudzu belongs to a group of plants (the Fabaceae family) that fix nitrogen so when the plant dies the soil is left fertilized.

Multiflora Rose
Species Characteristics
Scientific Name: Rosa multiflora
Growth Form: Perennial, deciduous, thicket forming shrub
Reproduction: Vegetative (stoloniferous), seeds
Season of Flowering: Late spring

Management Information
This thicket forming perennial produces large quantities of seed that is widely spread by birds. This seed can remain viable in the soil for years. In addition to reproduction via seed, multiflora rose reproduces vegetatively by rooting anywhere its branches come into contact with soil. Being that the plant is covered in thorns, hand pulling is difficult and so repeated moving is a more practical method of removal. Mow plants as close to the ground as possible then let plants grow to about two feet and then mow again. Repeat until root system is exhausted; this will likely take 3-6 mows during the growing season for a period of three years. For small areas, hand clipping can be used in a similar fashion to mowing. Also, if you have access to browsing animals, such as goats, they can be effective in removing rose especially on steep slope where other methods of removal may be difficult. Remember that goats are not selective and will eat other vegetation as well rose so protect anything you don’t want consumed or damaged. If you choose to use herbicide, use a systemic herbicide late in the season on the re-growth after a mow. As for all weeds, but especially for multiflora rose as its seeds remain viable for years, you will need to monitor for new seedlings and sprouts once the initial infestation is under control.

Nepalese Browntop
Species Characteristics
Scientific Name: Microstegium vimineum
Growth Form: Annual grass
Reproduction: Seed, vegetative (stoloniferous)
Season of Flowering: Late summer

Management Information
Also called Japanese stiltgrass, this very shade tolerant, annual grass spreads both by seed and by runners. High seed production and accelerated seed set in response to mowing are the biggest challenges presented by this grass. For small infestations the best approach for control is hand pulling. Allow plants to grow large enough to easily grip (but do not let them mature enough to go to seed!) and chose a day when soil is moist to make pulling easier. Be sure to pull as much of the root as possible. Pulling will disturb the soil and thus encourage germination of seedlings so expect to battle new plants. This can be frustrating but do not loose your resolve- the seed bank is being depleted with every wave of new germination. After initial pulling, an application of systemic herbicide to new seedlings is effective. When you have treated the infestation enough times to significantly reduce the number of new germinants, plant perennial non-grasses in the void. This will give you the option to apply a grass specific herbicide to control seedlings while filling the void to invite competition and suppress germination of Nepalese browntop seedlings. If you are comfortable with burning, it can be a good alternative to pulling especially if the infestation is large. Large infestations may also be controlled by mowing but because Nepalese browntop responds to mowing by rapidly flowering, an effective mowing can only be done once and as late in the season as possible. The late timing is important to reduce the time for seeds to develop before the plants die in the fall. Systemic herbicide application may be the most effective technique for large infestations because herbicide application has minimal soil disturbance. In places were the grass is mixed with desirable non-grasses, consider using a grass specific herbicide. Note that animals avoid consuming Nepalese browntop so control by grazing is ineffective.

Oriental Bittersweet
Species Characteristics
Scientific Name: Celastrus orbiculatus
Growth Form: Perennial, deciduous vine
Reproduction: Seed, vegetative (rhizomatous)
Season of Flowering: Spring

Management Information
Oriental bittersweet is a woody, perennial, climbing vine that spreads primarily by seeds that germinate in late spring. Its secondary form of reproduction is root sprout. Infestations can be controlled by hand pulling, mowing and herbicide application. Control is most successful when pulling or mowing is combined with a systemic herbicide application. If applying only an herbicide treatment, application will be most effective in the spring during active growth before flowering begins. If combining methods, first pull or mow plants in spring just as flowering begins, then wait until significant re-growth has occurred to apply herbicide. Pulling during flowering weakens the root system, eliminates reproduction and stimulates new growth that is more susceptible to herbicide than old growth. Repeated mowing has a similar effect to pulling. Mow plants during flowering, let plants re-grow then mow again, repeating until root system is exhausted. Application of systemic herbicide to the re-growth after mowing will speed along the process. To remove from trees, cut the vines away from the base of the host tree. Avoid pulling vines from the trees especially if they are large; the vines, or the branches that they are attached to, can fall and cause serious injury. Care should be taken when disposing of plant parts. Bagging plants to be taken off-site is recommended as it is difficult to kill roots and stems through drying because of their woody nature. Since seeds are this plant’s favored form of reproduction, it is especially important to monitor for new seedlings once the initial infestation is under control.

Princess Tree
Species Characteristics
Scientific Name: Paulownia tomentosa
Growth Form: Perennial, deciduous tree
Reproduction: Seed, vegetative (rhizomatous)
Season of Flowering: Spring

Management Information
Princess tree or paulownia is a prolific seed producer with a large root system. Typical time to flowering is between 8-10 years and the winged seeds are spread by wind. It easily re-sprouts from the root so killing the root system is important; systemic herbicide application will reach this goal most quickly. How to effectively apply herbicide depends upon the size of the tree. If trees are small, foliar application is best. If leaves are beyond reach by a sprayer, trees should be cut down and herbicide applied within a few minutes to the stump. Wet the entire surface of the stump completely and thoroughly. It is likely that the tree will still produce re-sprout after which a foliar herbicide application can be used. This tree can produce hundreds of thousands of seeds each year so be prepared to treat new seedlings once the initial infestation is under control. Seedlings can be killed with herbicide or pulled by hand.

Tree of Heaven
Species Characteristics
Scientific Name: Ailanthus altissima
Growth Form: Perennial, deciduous tree
Reproduction: Seeds, vegetative (rhizomatous)
Season of Flowering: Late spring

Management Information
This tree has an extensive root system and produces hundreds of thousands of seeds annually. The winged seeds are spread widely by wind and so new seedlings will need to be continually monitored for and eradicated. Seedlings can be killed with herbicide or pulled by hand. Tree of Heaven re-sprouts from the root prolifically so killing the root system is important. Root kill is accomplished most quickly using a systemic herbicide; how to do this most effectively depends upon the size of the tree. If trees are small, foliar application is best, but if leaves are beyond reach by a sprayer, trees should be cut down and herbicide be applied to the stump within a few minutes. The entire surface of the stump should be wet completely and thoroughly with herbicide. The tree will likely still produce some re-sprout and a foliar herbicide application can then be applied to the re-growth. Tree of Heaven comes in both male and female forms so if resources for control are limited, target female trees to reduce seed production.

Was this guide useful?
Once you’ve had a chance to use this guide, let us know if it was helpful. Were you able to control your weeds? Would you like to share your weed pictures? Send us your success stories as well as your suggestions for improvement by emailing information@riverlink.org or by calling (828) 252-8474. Thank you!

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