Southeast Exotic Pest Plant Council

Southeast Exotic Pest Plant Council Invasive Plant Manual

Common Name: Privet

Scientific Name: Ligustrum spp.

Several species of privet have been widely planted in Tennessee, primarily as a hedge in landscaping. They are difficult to distinguish and include common privet (L. vulgare L.), Chinese privet (L. sinense Lour.), and Japanese privet (L. japonicum Thunb.). All belong to the Oleaceae (Olive) family and easily escape cultivation to invade adjacent areas and form dense monocultural thickets.

Height: Privet can grow up to 5 m (16 ft) tall and to a diameter of 2.5-25 cm (1-10 in).

Bark: Privet bark is whitish-tan to gray in color and smooth in texture. Young branches are minutely hairy.

Twigs: Slender twigs are straight, rounded or four-angled below the nodes, and gray-green in color. Terminal buds are present.

Leaves: These deciduous or half-evergreen plants hold foliage into winter, but drop it before spring. Leaves are elliptic to ovate in shape. They are oppositely arranged on slender twigs and have 4-5 pairs of indistinct veins. Privet leaves are less than 6 cm (2.5 in) long, glabrous, leathery and thick, with a glossy cuticle on upper surface.

Flowers: The perfect flowers are small and white. Bloom time is June-July.

Fruit: The black, berrylike fruits contain 1-4 seeds and are borne in terminal clusters. Fruits are subglobose or ovoid and are 6-8 mm (0.25 in) long. The fruit clusters ripen during September and October and persist through the winter. Mature specimens can produce hundreds of fruit.

Life History

Privet is a perennial shrub that readily grows from seed or from root and stump sprouts. Privet escapes cultivation by movement of seed, which is eaten and subsequently transported by wildlife, particularly birds. The seeds are reported to have a low germination rate: 5%-27% in two tests.

Origin and Distribution

The privets are native to Europe, North Africa, and Asia. This ornamental landscape plant has been cultivated since ancient times and has been developed into several horticultural varieties. Date of introduction to the United States is unknown as is any record of introduction to Tennessee. Current range maps show L. vulgare (L.) in four central and six eastern Tennessee counties and L. sinense (Lour.) in three central and two eastern Tennessee counties; however both species are suspected to have wider distributions.

Similar Species

The leaves of the native shrub coralberry, Symphoricarpos orbiculatus(Moench.), are similar in shape to common privet. Coralberry is distinguished by its very slender twigs, deciduous leaves, red berries borne in axillary clusters, and the lack of a terminal bud.

Habitat

Privet is often seen along roadsides and other areas of disturbed soil at elevations less than 915 m (3000 ft). Privet also becomes established in old fields and landscapes that have abundant sunlight. Blunt-leaved privet,L. obtusifolium (Sieb. and Zucc.), was found invading an old field succession site in Illinois. The field had an average of more than 6,082 plants per ha (2.5 acres). Privet can also spread into forests, though it does not produce fruit in low light.


Photo by Ted Bodner


Photo by James H. Miller


Photo by James H. Miller


Photo by James H. Miller

Management Recommendations

Mechanical Controls

Mowing/Cutting: This method is appropriate for small initial populations or environmentally sensitive areas where herbicides cannot be used. Repeated mowing or cutting will control the spread of privet, but will not eradicate it. Stems should be cut at least once per growing season as close to ground level as possible.

Hand Pulling: Privet is effectively controlled by manual removal of young seedlings. Plants should be pulled as soon as they are large enough to grasp but before they produce seeds. Seedlings are best pulled after a rain when the soil is loose. Larger stems, up to 6 cm (2.5 in), can be removed using a Weed Wrench or similar uprooting tools. The entire root must be removed since broken fragments may resprout.

Biological Controls

Privet has no known biological controls. A foliage-feeding insect native to Europe, Macrophya punctumalbum, is a known pest. Privet is also susceptible to a fungal leaf spot, Pseudocercospora ligustri, and a common root crown bacteria, Agrobacterium tume-faciens.

Herbicidal Controls

Foliar Spray Method: This method should be considered for large thickets of privet where risk to non-target species is minimal. Air temperature should be above 65°F to ensure absorption of herbicides. The ideal time to treat is in late fall or early spring when many native species are dormant.

    Glyphosate: Apply a 2% solution of glyphosate and water plus a 0.5% non-ionic surfactant to thoroughly wet all leaves. Use a low pressure and coarse spray pattern to reduce spray-drift damage to non-target species. Glyphosate is a non-selective systemic herbicide that may kill non-target partially-sprayed plants.

    Triclopyr: Apply a 2% solution of triclopyr and water plus a 0.5% non-ionic surfactant, to thoroughly wet all leaves. Use a low pressure and coarse spray pattern to reduce spray-drift damage to non-target species. Triclopyr is a selective herbicide for broadleaf species. In areas where desirable grasses are growing under or around privet triclopyr can be used without non-target damage.

Cut Stump Method: This control method should be considered when treating individual bushes or where the presence of desirable species preclude foliar application. This treatment is effective as long as the ground is not frozen.

    Glyphosate: Horizontally cut privet stems at or near ground level. Immediately apply a 25% solution of glyphosate and water to the cut stump making sure to cover the entire surface.

    Triclopyr: Horizontally cut privet stems at or near ground level. Immediately apply a 25% solution of triclopyr and water to the cut stump making sure the entire surface is covered.

Basal Bark Method: This method is effective throughout the year as long as the ground is not frozen. Apply a mixture of 25% triclopyr and 75% horticultural oil to the basal parts of the shrub to a height of 30-38 cm (12-15 in) from the ground. Thorough wetting is necessary for good control; spray until run-off is noticeable at the ground line.

Bibliography

Core, E. L.;. Ammons, N. P. Woody plants in winter. Pacific Grove, CA: Boxwood Press. 182-183; 1992.

Ebinger, J. E. Exotic shrubs: a potential problem in natural area management in Illinois. Compendium on Exotic Species. Mukwonago, WI. The Natural Areas Association. Article 17, 1-3; 1992.

Faulkner, J. E. The use of prescribed burning for managing natural and historic resources in the Chickamauga and Chattanooga National Military Park. Knoxville, TN: The University of Tennessee. Thesis. 1987.

Johnson, W. T.; Lyon, H. H. Insects that feed on trees and shrubs. Ithaca, NY: Cornell University Press; 1988.

Radford, A. E.; Ahles, H.; Bell, C. R. Manual of the vascular flora of the Carolinas. Chapel Hill, NC: The University of North Carolina Press; 1968.

Rehder, A. Manual of cultivated trees and shrubs hardy in North America. 2nd ed. Portland, OR: Dioscorides Press, 783-784; 1986.

Sinclair, W. A.; Lyon, H. H.; Johnson, W. T. Diseases of trees and shrubs. Ithaca, NY: Cornell University Press, 86-88,156; 1987.

Swanson, R. E. A field guide to the trees and shrubs of the southern Appalachians. Baltimore MD: The Johns Hopkins University Press, 357-358; 1994.

USDA Forest Service. Woody Plant Seed Manual. Misc. Pub. No. 654. Washington, DC.; 1948.

Wofford, B. E. Range maps for the vascular plants of Tennessee. Knoxville, TN: The University of Tennessee. Unpublished.
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