Common Privet (Invasive Exotic Plants of North Carolina)

Common Privet

Ligustrum vulgare

Summary ⁶

Ligustrum vulgare (wild privet, also sometimes known as common privet or European privet), is a species of Ligustrum native to central and southern Europe, north Africa and southwestern Asia, from southern England and southwestern Sweden south to Morocco, and east to Poland and northwestern Iran.

Impacts and control ⁷

More info for the terms: fire management, hardwood, mesic, natural, presence, relict, restoration, shrub

Impacts: In many areas of North America, privet easily escapes cultivation and can quickly degrade native communities by forming dense monospecific stands [1]. In a survey of federal wilderness managers, privet was mentioned among "widely reported problem species" in Alabama, Arkansas, and Kentucky [32].

Japanese privet escapes into natural areas in southern North America where it can form "dense, impenetrable thickets" and displace native species [31]. One example is in natural areas around Austin, Texas, where Japanese privet has invaded intermittent stream bed and mesic woodland habitats. Its impacts include outcompeting native woody species such as wax mallow (Malvaviscus arborea var. drummondii), Mexican buckeye (Ungnadia speciosa), American beautyberry (Callicarpa americana), small palmleaf thoroughwort (Conoclinium greggii), pecan (Carya illinoensis), and Texas ash (Fraxinus texensis). Removal of Japanese privet from these areas has resulted in regrowth of other native species, including mescalbean sophora (Sophora secundiflora), Buckley oak (Quercus buckleyi), live oak (Quercus virginiana), southwestern bristlegrass (Setaria scheelei), toothleaf goldeneye (Viguiera dentata), white crownbeard (Verbesina virginica), Rio Grande palmetto (Sabal mexicana), rougeplant (Rivina humilis), and Drummond's woodsorrel (Oxalis drummondii) [53].

Chinese privet invades natural areas throughout much of southern and eastern North America. It has been reported as a problem weed on Nature Conservancy preserves in Alabama, Arkansas, Louisiana, Georgia, Florida, Mississippi, Tennessee, and North Carolina [1]. Chinese privet establishes monospecific stands that dominate the forest shrub layer and shade out herbaceous plants, altering species composition and community structure [11,31,68]. Increasing abundance of Chinese privet in the understory of eastern bottomland forests may hinder regeneration of native hardwood species [4].

An example of the impacts of Chinese privet on native plant diversity is in southern Florida, where it has invaded undisturbed relict slope hammock habitat, threatening to displace the rare Miccosukee gooseberry (Ribes echinellum) [64]. Miccosukee gooseberry is federally listed as threatened [63] and state listed as endangered in Florida [15].

Impacts of European privet on native North American flora are mixed. It has been reported as a problem weed on Nature Conservancy preserves in Arkansas, Tennessee, and Ohio [1], but there are fewer reports of negative impacts from invasive European privet in North America than for Chinese privet. Gayek and Quigley [18] describe valley bottoms in a southwestern Ohio mixed mesophytic forest where European privet has been growing for at least 40 years. Their studies indicate that European privet generally does not compete well in the understories of these forests. Even in moist valley bottoms where it establishes mature stems, European privet coexists with a variety of native perennials and spring "wildflowers" [18]. More research is needed to determine where escaped European privet poses the greatest threat to North American natural areas.

Control: Perhaps the most important aspect of controlling privet is managing sprouting that often occurs subsequent to initial control treatments (see Asexual regeneration). Control methods that remove or damage aboveground stems, such as mechanical cutting or prescribed burning, will likely cause sprouting. Subsequent monitoring and repeated treatments may be necessary to eliminate sprouting stems.

Prevention: Preventing the influx of privet seed from relatively distant sources may be impossible due to dispersal by birds. Preventing establishment of dense, seed-producing populations in managed natural areas will increase the probability of successful restoration programs [1]. Frequent monitoring may be necessary in areas near a privet seed source or in areas that were recently treated to control existing privet infestations. Young Chinese privet seedlings (stem diameter < 1 inch (25 mm) and height < 8 inches (20 cm)) are able to produce "substantial" amounts of fruit [72]. Young privet stems of sprout origin might also be capable of contributing seed soon after control treatments.

Integrated management: No information

Physical/mechanical: Seedlings can be removed by hand-pulling. When hand-pulling seedlings, the entire root system must be extracted to prevent sprouting. Established seedlings become increasingly difficult to hand-pull because of a strong root system [68].

Mowing and/or cutting can reduce the spread of privet by preventing seed production. Repeated cutting may eventually eradicate privet [1]. Stems larger than 1 inch (2.5 cm) in diameter may be most easily controlled by cutting close to ground level and applying herbicides to the cut stumps [30,53,68]. Cutting stems without accompanying herbicide treatment will likely promote growth from sprouting. Even with repeated follow-up cutting, mechanical control alone may be difficult [68].

Fire: See Fire Management Considerations.

Biological: No information

Grazing/browsing: Domestic goats can provide some control, provided privet has not grown beyond browseline [1].

Chemical: Invasive privet can often be effectively controlled by painting cut stumps with herbicides. Areas where this method may be particularly desirable include sparse infestations of large stems, places where stems are concentrated, such as fence lines, or habitats where the presence of desirable native species precludes foliar application [26].

Foliar spraying can also be effective, particularly for dense populations. Late fall or early spring are the best times for foliar spraying, since privet is likely to be biologically active but native species are dormant. Applying herbicide and oil solution to basal stem bark may also kill privet [1].

Below is a list of herbicides that have been tested and judged effective for controlling privets in North America, as well as some special considerations for specific control techniques. There is no information available, as of this writing (2003), concerning chemical control of Amur privet. Japanese privet Chinese privet European privet Chemical(s) Special Considerations Chemical(s) Special Considerations Chemical(s) Special Considerations imazapyr effective for painting cut stumps [53] imazapyr [1,35] effective for painting cut stumps [1] 2,4-D/picloram effective for painting cut stumps [26] glyphosate most effective when applied at bud break or soon thereafter [1] glyphosate [35,68] apply to foliage in late fall after native plant foliage has abscised [1,68] glyphosate effective for painting cut stumps [1] triclopyr [1] triclopyr/picloram effective for painting cut stumps [26] metsulfuron [26,35] metsulfuron [26] glyphosate/X-45 [26,31] effective for painting cut stumps or for foliar application [31]

For more information regarding appropriate use of herbicides against invasive plant species in natural areas, see The Nature Conservancy's Weed control methods handbook. For more information specific to herbicide use against privet, see The Nature Conservancy's Element Stewardship Abstract web page for Ligustrum spp. Cultural: No information

Habitat characteristics ⁸

More info for the terms: adventitious, mesic

Privets occupy a variety of habitats in North America but may not tolerate dry soils well.

Information about site characteristics for Japanese privet is sparse. It is mostly mentioned as occurring in mesic and/or disturbed habitats [4,20,31,75].

Chinese privet occurs within a variety of sites throughout its North American range. It is adapted to an assortment of soil types, is somewhat drought tolerant, and has low soil fertility requirements. Chinese privet is most competitive on moist, well-drained soils [31]. It is frequently mentioned from moist or "nonxeric" sites [1,4,10,14,20,31,40,46,59,68], and ruderal or edge habitats [1,9,20,31,43,59,68,75].

Although Chinese privet apparently does not grow well on poorly drained soils [31], it appears to be tolerant of short-term flooding. In a greenhouse study, seedlings were subjected to shallow flooding and deep flooding treatments for 80 days. While gas exchange and growth were lower in flooded compared with nonflooded treatments, morphological adaptations (i.e. lenticels and adventitious roots) led to ≥75% survival in 5 of 6 flood treatments [4].

European privet also has been recorded from a variety of sites within North America. It has been mentioned as occurring within old fields, glades, barrens, woodlands, and closed-canopy forests [1,57]. Forest sites where European privet has been described include riparian, bottomland, upland, and cove forests [1,47]. In the upper Midwest, it escapes to "disturbed ground and forests, dry or damp" [69], as well as "more or less undisturbed woodland" [3].

Despite the apparent ubiquitous nature of European privet, there is evidence that its distribution may be limited by moisture availability in some areas. In a mixed mesophytic forested valley in southwestern Ohio, European privet was unable to establish mature stands on dry rocky slopes, despite successful recruitment of seedlings from mature seed sources in the moist valley bottom. It was suggested that the dearth of mature stems on the steep valley slopes was due, in part, to the dry rocky soils [18].

Sources and Credits

Jan Ševčík, no known copyright restrictions (public domain), https://www.biolib.cz/IMG/GAL/102825.jpg
(c) Radio Tonreg, some rights reserved (CC BY), http://www.flickr.com/photos/63169246@N00/7261455316
Wikimedia Commons, no known copyright restrictions (public domain), https://upload.wikimedia.org/wikipedia/commons/1/1e/Ligustrum_vulgare.jpg
(c) Hermann Falkner, some rights reserved (CC BY-NC-SA), http://farm7.static.flickr.com/6105/6332734742_23381b8ba9_o.jpg
(c) Wikimedia Commons, some rights reserved (CC BY-SA), https://upload.wikimedia.org/wikipedia/commons/f/f4/Wilde_liguster_%28Ligustrum_vulgare%29.jpg
Adapted by Kate Wagner from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Ligustrum_vulgare
Public Domain, http://eol.org/data_objects/24636945
Public Domain, http://eol.org/data_objects/24636936

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Common Privet

Summary 6

Impacts and control 7

Habitat characteristics 8