Privet as an invasive plant

Last updated

Privets are any of a number of shrubs or trees in the genus Ligustrum, many of which are invasive. The genus contains about 50 species [1] native to the Old World and Australasia. [2] Many members of the genus are grown as ornamental plants in parts of the world.

Contents

Several species of privet have become a nuisance in regions outside their ranges. In these conditions they are most commonly found wherever there is disturbed soil, soil that is physically perturbed from its natural state through fire or mechanical machinery, such as along fencerows, old fields, ditches, and forest margins. [3] Privet grows particularly well in riparian forests, which are found throughout the Southeastern United States. [4] Although tolerant of varying soil and light conditions, including a tolerance for shade, privet survives best in mesic soil with abundant sunlight. [5]

Economic and cultural effects

Privet is considered a huge problem in New Zealand and the east coast of Australia ( Ligustrum lucidum , Ligustrum sinense and Ligustrum vulgare [6] ). It is banned from sale or cultivation in New Zealand because its pollen is known to cause asthma and eczema in sufferers. Privet can be removed by contacting local government agencies to report its presence. [7] but in Auckland it is only a surveillance pest plant in the 2012 Regional Pest Management Strategy. The NZ Weedbusters site provides guidance on how to get rid of the plant. [8]

When privet is invasive species, the cost of controlling and removing privet is economically detrimental, something that is problematic for conservation efforts. [5] The annual cost of removing Chinese privet in the United States is estimated to be $737 per acre when a mulching machine and two-person herbicide application crew are employed. [9] The cost for foliar glyphosate applications on privet is approximately $130 per acre for chemical and surfactant treatments. [9]

Invasiveness

Privet is a successful invasive species because of its ability to outcompete and therefore displace native vegetation. [5] This competitive superiority to native vegetation is connected with the plant's ability to adapt to different light conditions. [10] For example, in low light environments, privet is able to produce fewer and larger ramets than its competitors. [10] These larger ramets make privet more tree-like, making privet better able to compete for light than its more shrub-like native counterparts. [10] Privet is an ideal invasive species because it reproduces both sexually and asexually. [5] Through sexual reproduction, privet produces seeds that are easily dispersed by wind and animals. [5] These seeds can rapidly colonize disturbed soil such as that perturbed by fires, forest clearings, erosion, or abandoned agricultural land. [5] Privet matures quickly, which allows for a short generation cycle and even greater dispersal. [5] The roots of privet can reproduce asexually through root suckers. [5] This vegetative reproduction makes privet difficult and costly to control because root fragments left in the soil can sprout and grow new plants. [5]

One reason why privet is so invasive in the United States is because it has few native shrub competitors. [11] In a sense, privet is invading and exploiting an open niche within the southern U.S. floodplain ecosystem. [11] Prior to privet invasion much of the native land was clear and open; currently, privet forms a dense thicket which chokes out other, usually native, plant life. [11] Thus, privet is believed to be phylogenetically distinct compared to its native cousins. [11]

Ecological impact in the U.S.

Introduction

All nine species of privet currently in the southeast U.S. are invasive. [3] The first species of privet was introduced into the United States in the 1700s as an ornamental plant used as a hedge or foliage for gardens. [3] Glossy privet arrived in the U.S. in 1794, Chinese privet in 1825, Japanese privet in 1845, California privet in 1847, and Amur privet in 1860. [3] Privets escaped cultivation in the early 1900s, but became widely naturalized during the 1950s-1970s or later. [5] Currently privet is designated as a foreign invasive plant in Alabama and Georgia and considered a severe threat in North Carolina and Florida. [3] It is estimated that Chinese privet alone occupies over one million hectares of land across 12 states ranging from Virginia to Florida and west to Texas. [4]

The full ecological effect of privet is still being studied. However, data suggest that forests containing large amounts of privet tend to have fewer trees, less shrub diversity, and decreased density of herbaceous plants. [12] When introduced to an ecosystem, privet grows quickly and, given time, will produce a thick layer under the forest canopy preventing sunlight from reaching the native plants below. [12] In some cases, this can drive native populations to extinction. [5] If left unchecked, privet may result in large-scale ecosystem modification and an overall loss of native species diversity and richness. [4] The Sierra Chicas of Cordoba have experienced just such a widespread landscape change since 1970. [4]

In a study by Greene and Blossey using field observations and a transplant experiment, a significant negative correlation was found between percent Chinese privet cover and herbaceous cover, species richness, and plant height. [11] In a comparison of two experimental gardens, each with four native plant species, the plot with Chinese privet contained almost entirely nonnative plants after 64 weeks. [11] Out of approximately twenty plants per species, only single individuals of Acer negundo , Chamaenerion latifolium and C. tribuloides survived the entire study when in the presence of Chinese privet. [11] Surviving plants had lower leaf counts and stunted height relative to their counterparts in privet-absent plots. [11] None of the Boehmeria cylindrica survived. [11]

Insects are greatly affected by the proliferation of invasive species such as privet. [13] For example, one study found the abundance and diversity of butterflies increased following privet removal to almost the same abundance as that of a similar forest community, with no history of privet invasion. [13] In a study conducted in Georgia, privet was found to decrease the diversity of native honeybee colonies. [12] Plots removed of privet resulted in four times as many bee species as control plots in which privet was not removed. [12] Traps placed in undisturbed forest plots with no history of privet caught an average of 210 bees from 34 species, while traps placed in privet-infested plots caught an average of 35 bees from only 9 species. [12]

Another example of how privet can have a negative ecological impact in ecological communities is its ability to threaten endangered species. [14] For example, privet threatens the Miccosukee gooseberry, a native plant species that privet is similar to, by encroaching on the gooseberry's habitat and slowly displacing it. [15]

Biological species invasion is considered a main component of global ecosystem change due to changes in biogeochemical cycles and disturbance regimes. [16] Invasive species such as privet are known to alter the dominant vegetation type, soil properties, animal behavior, and the natural cycling of resources. [16] For example, Chinese privet increases the decomposition rate of leaf litter by 2.6-fold in riparian forests. [17]

However, because the usual method employed to study the impact of privet is to compare invaded and non-invaded areas, available data may be inaccurate. [4] This is because these types of comparison studies have trouble controlling for abiotic and biotic habitat conditions that could be negatively affecting native plant growth. [11]

Effect of climate change

Evidence suggests that climate changes, brought about by increased CO2 concentrations, will increase the spread and proliferation of privet. [18] Climate change is predicted to increase competition between native and invasive plants. Additionally, the increased temperatures that result from climate change are predicted to expand the range of plants typically restricted to the deep south where it is warm and moist. [18] In a projection based on the current and predicted CO2 levels, temperature, and precipitation, it was predicted that by the year 2100 privet will have spread as far north as Maine, sweeping across the mid-western United States into Nebraska. [18] Thus, states that are currently free from privet invasion (Michigan, Ohio, Indiana, Illinois, Kentucky, Virginia, Pennsylvania, etc.) are all predicted to become invaded with privet within the next 100 years unless either privet is contained or conservation efforts decrease the effect of pollution on climate change. [18]

Control and removal methods

Methods of control

The same qualities that allow privet to outcompete native species make it extremely difficult to control and eradicate. [5] Privet is manageable with mowing or cutting consistently, as closely to the ground as possible. [19] This will prevent the spread of the privet but will not eradicate it. [19] Even methods such as controlled burning have proven ineffective and actually aid privet growth because privet recovers better than native plants from controlled burns. [19]

Mechanical removal of privet, especially for younger plants or smaller areas of growth, can be effective; however, all of the root must be removed to prevent root re-sprouting. [5] Mechanical removal can prove difficult for more large-scale invasions. [5] When such large invasions occur in the natural environment, herbicide use is usually avoided due to the negative impacts on native plants. [5] Thus, the use of many workers or heavy machinery such as bulldozers is the most effective option. [5] However, the soil disturbance and resulting erosion are important considerations when using such measures. [5]

When herbicide use is warranted, several methods have proven effective. [5] In all cases, soil disturbance following herbicide treatment is inadvisable. [19] This is due to privet's preference for disturbed soils and its increased ability to compete in such an environment. [5] The length of time that the soil must be left undisturbed varies with the treatment. [5] Foliar applications of glyphosate, cut-stump applications of glyphosate or triclopyr, and basal bark treatments for stems less than 0.5 inches is effective. [19]

The foliar treatments are most effective against dense thickets of privet. [5] The best time for such treatments are in late fall and early spring when many of the native species are dormant. [5] Care must be used with such an application to avoid spraying non-target plants. [5] This treatment is generally considered to be less effective than the cut-stump and basal bark methods. [5]

The cut-stump method is most useful when treating single plants. [5] This method consists of thoroughly covering the stump of a recently cut plant with herbicides, such as glyphosate and triclopyr. [19] The effectiveness of this treatment is increased by cutting a hole into the surface of the stump. [19] Use of this treatment when the plant breaks the dormant stage as well as when the ground is frozen is advised against as it greatly reduces effectiveness. [5]

The basal bark treatment consists of application of herbicide to all basal parts of the plant below 12-15 inches. [19] The bark must be thoroughly wet with herbicide for this treatment to be most effective. [19] The USDA suggests that 25% triclopyr and 75% horticultural oil is the most effective herbicide composition for basal bark treatments. [5]

The first known biological control of privet is the privet lace bug (Leptoypha hospita), which has been deployed in New Zealand. [20]

Agencies working to control privet

The Federal Interagency Committee for the Management of Noxious and Exotic Weeds (FICMNEW) engages with public and private organizations in the effort to combat noxious and exotic weeds, including Chinese and European privet. [21] Privet is monitored by the US Forest Service's Invasive Species Program while the National Park Service deploys Exotic Plant Management Teams. [22] Each team has jurisdiction over ten national parks and works with local volunteers, contractors, and service organizations. [22]

These agencies work to eliminate, contain, and/or remove privet because many areas invaded by privet, such as the Piedmont floodplains, are important areas of biodiversity, carbon storage, and resource production. [11]

See also

Related Research Articles

<span class="mw-page-title-main">Kudzu</span> Group of climbing, coiling, and trailing perennial vine

Kudzu, also called Japanese arrowroot or Chinese arrowroot, is a group of climbing, coiling, and trailing deciduous perennial vines native to much of East Asia, Southeast Asia, and some Pacific islands, but invasive in many parts of the world, primarily North America.

<span class="mw-page-title-main">Privet</span> Genus of flowering plants in the family Oleaceae

A privet is a flowering plant in the genus Ligustrum. The genus contains about 50 species of erect, deciduous or evergreen shrubs, sometimes forming small or medium-sized trees, native to Europe, north Africa, Asia, many introduced and naturalised in Australasia, where only one species, Ligustrum australianum, extends as a native into Queensland. Some species have become widely naturalized or invasive where introduced. Privet was originally the name for the European semi-evergreen shrub Ligustrum vulgare, and later also for the more reliably evergreen Ligustrum ovalifolium and its hybrid Ligustrum × ibolium used extensively for privacy hedging, though now the name is applied to all members of the genus. The generic name was applied by Pliny the Elder to L. vulgare. It is often suggested that the name privet is related to private, but the OED states that there is no evidence to support this.

<i>Bromus tectorum</i> Species of grass

Bromus tectorum, known as downy brome, drooping brome or cheatgrass, is a winter annual grass native to Europe, southwestern Asia, and northern Africa, but has become invasive in many other areas. It now is present in most of Europe, southern Russia, Japan, South Africa, Australia, New Zealand, Iceland, Greenland, North America and western Central Asia. In the eastern US B. tectorum is common along roadsides and as a crop weed, but usually does not dominate an ecosystem. It has become a dominant species in the Intermountain West and parts of Canada, and displays especially invasive behavior in the sagebrush steppe ecosystems where it has been listed as noxious weed. B. tectorum often enters the site in an area that has been disturbed, and then quickly expands into the surrounding area through its rapid growth and prolific seed production.

<i>Centaurea diffusa</i> Species of flowering plant

Centaurea diffusa, also known as diffuse knapweed, white knapweed or tumble knapweed, is a member of the genus Centaurea in the family Asteraceae. This species is common throughout western North America but is not actually native to the North American continent, but to the eastern Mediterranean.

<i>Melilotus albus</i> Species of flowering plant in the bean family Fabaceae

Melilotus albus, known as honey clover, white melilot (UK), Bokhara clover (Australia), white sweetclover (US), and sweet clover, is a nitrogen-fixing legume in the family Fabaceae. Melilotus albus is considered a valuable honey plant and source of nectar and is often grown for forage. Its characteristic sweet odor, intensified by drying, is derived from coumarin.

<i>Ardisia crenata</i> Species of plant

Ardisia crenata is a species of flowering plant in the primrose family, Primulaceae, that is native to East Asia. It is known by a variety of names such as Christmas berry, Australian holly, coral ardisia, coral bush, coralberry, coralberry tree, hen's-eyes, and spiceberry. A. crenata is a compact shrub that reaches 1 metre (3.3 ft), often with a single stem. Leaves are dark green, thick, glossy, and have tightly waved edges The flowers are small, white or reddish, fragrant, and form clusters. The fruit is a glossy, bright red drupe. The seeds are able to germinate under a dense canopy and are dispersed by birds and humans.

<i>Miconia crenata</i> Species of flowering plant

Miconia crenata, commonly called soapbush, clidemia or Koster's curse, is a perennial shrub. It is an invasive plant species in many tropical regions of the world, causing serious damage.

<i>Ligustrum sinense</i> Species of plant

Ligustrum sinense is a species of privet native to China, Taiwan and Vietnam, and naturalized in Réunion, the Andaman Islands, Norfolk Island, Costa Rica, Honduras, Panamá and much of the eastern and southern United States. The name "Chinese privet" may also refer to Ligustrum lucidum.

<i>Ligustrum lucidum</i> Species of tree

Ligustrum lucidum, the broad-leaf privet, Chinese privet, glossy privet, tree privet or wax-leaf privet, is a species of flowering plant in the olive family Oleaceae, native to the southern half of China and naturalized in many places. The name "Chinese privet" is also used for Ligustrum sinense.

<i>Lonicera maackii</i> Species of plant in the family Caprifoliaceae native to western Asia

Lonicera maackii, the Amur honeysuckle, is a species of honeysuckle in the family Caprifoliaceae that is native to temperate eastern Asia; specifically in northern and western China south to Yunnan, Mongolia, Primorsky Krai in southeastern Siberia, Korea, and, albeit rare there, central and northern Honshū, Japan.

<i>Ligustrum japonicum</i> Species of flowering plant

Ligustrum japonicum, known as wax-leaf privet or Japanese privet is a species of Ligustrum (privet) native to central and southern Japan and Korea. It is widely cultivated in other regions, and is naturalized in California and in the southeastern United States from Texas to Virginia.

<i>Cinchona pubescens</i> Species of plant

Cinchona pubescens, also known as red cinchona and quina (Kina), is native to Central and South America. It is known as a medicinal plant for its bark's high quinine content- and has similar uses to C. officinalis in the production of quinine, most famously used for treatment of malaria.

<i>Ligustrum ovalifolium</i> Species of plant

Ligustrum ovalifolium, also known as Korean privet, California privet, garden privet, and oval-leaved privet, is a species of flowering plant in the olive family Oleaceae. The species is native to Japan and Korea.

<i>Ligustrum vulgare</i> Species of flowering plant


Ligustrum vulgare is a species of Ligustrum native to central and southern Europe, north Africa and southwestern Asia, from Ireland and southwestern Sweden south to Morocco, and east to Poland and northwestern Iran.

<i>Rhamnus cathartica</i> Species of flowering plant in the buckthorn family Rhamnaceae

Rhamnus cathartica, the European buckthorn, common buckthorn, purging buckthorn, or just buckthorn, is a species of small tree in the flowering plant family Rhamnaceae. It is native to Europe, northwest Africa and western Asia, from the central British Isles south to Morocco, and east to Kyrgyzstan. It was introduced to North America as an ornamental shrub in the early 19th century or perhaps before, and is now naturalized in the northern half of the continent, and is classified as an invasive plant in several US states and in Ontario, Canada.

<span class="mw-page-title-main">Riparian buffer</span> Vegetated area near a stream, usually forested

A riparian buffer or stream buffer is a vegetated area near a stream, usually forested, which helps shade and partially protect the stream from the impact of adjacent land uses. It plays a key role in increasing water quality in associated streams, rivers, and lakes, thus providing environmental benefits. With the decline of many aquatic ecosystems due to agriculture, riparian buffers have become a very common conservation practice aimed at increasing water quality and reducing pollution.

<i>Vincetoxicum nigrum</i> Species of plant

Vincetoxicum nigrum, a species in the family Apocynaceae, also known as black swallow-wort, Louise's swallow-wort, or black dog-strangling vine, is a species of plant that is native to Europe and is found primarily in Italy, France, Portugal, and Spain. It is an invasive plant species in the northeastern United States, parts of the Midwest, southeastern Canada, and California. In 2020, wild plants were found in Timaru, New Zealand.

<span class="mw-page-title-main">Riparian-zone restoration</span> Ecological restoration of river banks and floodplains

Riparian-zone restoration is the ecological restoration of riparian-zonehabitats of streams, rivers, springs, lakes, floodplains, and other hydrologic ecologies. A riparian zone or riparian area is the interface between land and a river or stream. Riparian is also the proper nomenclature for one of the fifteen terrestrial biomes of the earth; the habitats of plant and animal communities along the margins and river banks are called riparian vegetation, characterized by aquatic plants and animals that favor them. Riparian zones are significant in ecology, environmental management, and civil engineering because of their role in soil conservation, their habitat biodiversity, and the influence they have on fauna and aquatic ecosystems, including grassland, woodland, wetland or sub-surface features such as water tables. In some regions the terms riparian woodland, riparian forest, riparian buffer zone, or riparian strip are used to characterize a riparian zone.

<i>Torilis japonica</i> Species of flowering plant

Torilis japonica, the erect hedgeparsley, upright hedge-parsley or Japanese hedge parsley, is a herbaceous flowering plant species in the celery family Apiaceae. Japanese hedge parsley is considered both an annual and biennial plant depending on the biogeographical location. This means Japanese hedge parsley can complete its life cycle in either one or two growing seasons depending on habitat. Japanese hedge parsley is typically found in areas with disturbed soils, pastures, margins, open woodland, near waste sites, or right-of-way habitats. It can withstand a variety of habitats, thriving in partial and full shaded areas, but also withstanding habitats with full sunlight penetration. It is considered an aggressive invasive species in North America; invading a wide range of habitats due to its environmental tolerance and tendency to outcompete native vegetation. This species is considered a threat in several areas that causes problems relating to overall environmental health and stability. Aside from its environmental implications, T. japonica has potential to fight several cancers through a terpene it produces called Torilin, extracted from its fruits.

<span class="mw-page-title-main">Kudzu in the United States</span> Plant invasion

Kudzu is an invasive plant species in the United States, introduced from Asia with devastating environmental consequences, earning it the nickname "the vine that ate the South". It has been spreading rapidly in the Southern United States, "easily outpacing the use of herbicide, spraying, and mowing, as well increasing the costs of these controls by $6 million annually". Estimates of the vine's spread vary, from the United States Forest Service's 2015 estimate of 2,500 acres per year to the Department of Agriculture's estimate of as much as 150,000 acres annually.

References

  1. ↑ Webb, C. J.; Sykes, W. R.; Garnock-Jones, P. J. 1988: Flora of New Zealand. Vol. IV. Naturalised Pteridophytes, Gymnosperms, Dicotyledons. 4. Christchurch, New Zealand, Botany Division, D.S.I.R.
  2. ↑ RHS A-Z encyclopedia of garden plants. United Kingdom: Dorling Kindersley. 2008. p. 1136. ISBN   978-1405332965.
  3. 1 2 3 4 5 Maddox, V., J. Byrd, Serviss, B. (2010). Identification and Control of Invasive Privets (Ligustrum spp.) in the Middle Southern United States. Invasive Plant Science and Management. 3:482-488.
  4. 1 2 3 4 5 Hanula, J.L, Horn, S., Taylor, J.W. (2009). Chinese privet (Ligustrum sinense) Removal and its Effect on Native Plant Communities of Riparian Forests. Invasive Plant Science and Management 2:292-300. doi : 10.1614/IPSM-09-028.1
  5. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 Urbatch, L. Chinese Privet: Plant Guide. USDA and NRCS.<https://plants.usda.gov/DocumentLibrary/plantguide/pdf/pg_lisi.pdf>Retrieved 19 April 2022
  6. ↑ van Oosterhout, Elissa; Mowatt, J; Smith, Leon; Johnson, Stephen (2010). "Privet – broad-leaf, small-leaf and European (Ligustrum species)". NSW Department of Primary Industries.
  7. ↑ "Environment Waikato on Privet".
  8. ↑ "Tree Privet".
  9. 1 2 Environmental Assessment: Zebra Project (Timber Scale). (2010) USDA. <http://a123.g.akamai.net/7/123/11558/abc123/forestservic.download.akamai.com/11558/www/nepa/63900_FSPLT1_026073.pdf> Retrieved 15 March 2013
  10. 1 2 3 Lornalkfosko[ris, Jeffrey L. Walck, Hidayati, S.N. (2002). Growth and Reproduction of the Invasive Ligustrum sinense and Native Forestiera ligustrina (Oleaceae): Implications for the Invasion and Persistence of a Nonnative Shrub. International Journal of Plant Sciences. 163: 1001-1010.
  11. 1 2 3 4 5 6 7 8 9 10 11 Greene, B.T., Blossey, B. (2011). Lost in the weeds: Ligustrum sinense reduces native plant growth and survival. Biological Invasions. 14:139-150
  12. 1 2 3 4 5 Zhang, Y., Hanula, J., Horn, S., Braman, S.K., Sun, J. (2011). Biology of ‘'Leptoypha hospita'’ (Hemiptera: Tingidae), a Potential Biological Control Agent of Chinese Privet. Ann. Entomol. Soc. Am. 104: 1327-1333.
  13. 1 2 Hanula, J. L., Horn, S. (2011). Removing an invasive shrub (Chinese privet) increases native bee diversity and abundance in riparian forests of the southeastern United States. Insect Conservation and Diversity 4: 275-283.
  14. ↑ Zhang, Y., Hanula, J., Horn, S., Braman, S.K. and J. Sun. 2011. Biology of Leptoypha hospita (Hemiptera: Tingidae), a Potential Biological Control Agent of Chinese Privet. Ann. Entomol. Soc. Am. 104: 1327-1333.
  15. ↑ Langeland, K. A., Burks, K.C. (1998). Identification and biology of non-native plants in Florida's natural areas. University of Florida, Gainesville. 165 pp.
  16. 1 2 Gavier-Pizarro, G.I., T. Kuemmerle, L.E. Hoyos, S.I. Stewart, C.D. Huebner, N.S. Keuler, and Radeloff, V.C. (2012). Monitoring the invasion of an exotic tree (Ligustrum lucidum) from 1983 to 2006 with landsat TM/ETM + satellite data and support vector machines in Córdoba, Argentina. Remote Sensing of Environment 122: 134-145.
  17. ↑ Mitchell, J. D., Lockaby, B.G., Brantley, B.F. (2011). Influence of Chinese Privet (Ligustrum sinense) on Decomposition and Nutrient Availability in Riparian Forests. Invasive Plant Science and Management 4:437-447.
  18. 1 2 3 4 Bradley, B.A., Wilcove, D.S., Oppenheimer, M. (2010). Climate change increases risk of plant invasion in the eastern United States. Biological Invasions 12:1855–187
  19. 1 2 3 4 5 6 7 8 9 Chinese Privet. (2013). Center for Aquatic and Invasive Plants. <http://plants.ifas.ufl.edu/node/231>Retrieved 15 March 2013>
  20. ↑ "Privet lace bug shows early promise". Weed Biocontrol. Landcare Research (76): 5. May 2016. Retrieved 2 February 2017.
  21. ↑ Federal Interagency Committee for the Management of Noxious and Exotic Weeds <http://www.fs.fed.us/ficmnew/index.shtml> Retrieved 15 March 2013
  22. 1 2 National Park Service. <http://www.nature.nps.gov/biology/invasivespecies/EPMT_teams.cfm>Retrieved 15 March 2013
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.