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thorny olive

Elaeagnus pungens

Description 8

More info for the terms: shrub, shrubs

Botanical description: This description covers characteristics that may be relevant to fire ecology and is not meant for identification. Keys for identification are available (e.g., [22,42]).

Thorny-olive is a multistemmed, freely branched, dense shrub [22,37,42]. It may reach 25 feet (7.6 m) tall and 15 feet (4.6 m) wide [15,37]. Once established, thorny-olive produces prolific, fast-growing stem sprouts, which allow shrubs to increase in size and "scramble" through neighboring vegetation [22,37]. Stem bark is armed with "rather nasty", 2- to 3-inch (5-8 cm) long thorns [15]. Leaves are simple, evergreen, arranged alternately, and typically measure 1.6 to 4 inches (4-10 cm) long and less than half as wide [15,42]. The undersides of leaves are ashy white and flecked with brown scales [60]. Thorny-olive produces tubular flowers that are about 1 cm long and occur in clusters of up to 3 [37]. Fruits are single-seeded drupes that are 1 to 1.5 cm long [37,42].

Impacts and control 9

More info for the terms: fire management, invasive species, natural, prescribed fire, shrubs, tree

Impacts: Thorny-olive's growth rate and habit suggest that infestations could exclude native vegetation and restrict human and wildlife movements. Rapid thorny-olive growth has been reported by many [5,15,37]. One horticultural reference suggests that "fast" is an inadequate description of thorny-olive's growth rate [15], while another describes growth as "aggressive" and "rampant" [21]. Thorny-olive produces dense, thorny stems, which can climb into other vegetation. Dirr [15] described the thorny-olive growth form as "a genuine horror" and observed thorny-olive stems growing 30 feet (9 m) into nearby tree branches. Photo © Rebekah D. Wallace, Bugwood.org

While it seems that dense, rapid, and sometimes climbing growth would inevitably shade other vegetation, reduce native plant recruitment, and restrict human and animal movements, the citations that suggest such [11,35] lack documentation of these effects. Some suggest that thorny-olive could hybridize with other oleasters (Elaeagnus spp.) in the United States [35], but hybrids were not reported in the reviewed literature.

Although impacts have not been documented in any detail, many southern states treat thorny-olive as a serious threat to native plant communities. When invasive shrubs of Kentucky were compared, thorny-olive had many characteristics in common with the most widespread invasive shrubs, suggesting it could become widespread in the state [7]. As of 2008, thorny-olive was considered a severe threat by the South Carolina Exotic Pest Plant Council. Severe threat species are those known to severely threaten the composition, structure, or function of natural areas [46]. Thorny-olive is also listed as a moderate or significant threat to natural areas by other southern states including Tennessee [49], Georgia [20], and Florida [18].

Control: Studies involving the control of thorny-olive were generally lacking, but there are some recommendations with regard to the timing of control. Control measures prior to fruit ripening are recommended to limit seed dispersal [11]. Defoliation control measures may be more successful in the fall than in the spring. In a nursery study, all thorny-olive plants survived spring defoliation, and growth of spring-defoliated plants was not significantly different from that of controls. However, just 3 of 8 plants survived fall defoliation in "good condition" [32].

Control of biotic invasions is most effective when it employs a long-term, ecosystem-wide strategy rather than a tactical approach focused on battling individual invaders [36]. In all cases where invasive species are targeted for control, no matter what method is employed, the potential for other invasive species to fill their void must be considered [9].

Prevention: Establishment and spread of thorny-olive may be prevented by restricting its sale and use for landscape and roadside plantings in or near invasible habitats. As of 2009, thorny-olive was still available for sale in nurseries. The use of thorny-olive in ornamental, hedgerow, and roadside plantings is a major means for dispersal [11,37]. In a 1984 edition of the Pacific Horticulture magazine, thorny-olive was highlighted as an "excellent plant for the California landscape" [30], an area in which it may not occur outside of cultivation (as of 2011).

It is commonly argued that the most cost-efficient and effective method of managing invasive species is to prevent their establishment and spread by maintaining "healthy" natural communities 36,44 and by monitoring several times each year [27]. Managing to maintain the integrity of the native plant community and mitigate the factors enhancing ecosystem invasibility is likely to be more effective than managing solely to control the invader [25]. Weed prevention and control can be incorporated into many types of management plans, including those for logging and site preparation, grazing allotments, recreation management, research projects, road building and maintenance, and fire management [53]. See the Guide to noxious weed prevention practices [53] for specific guidelines in preventing the spread of weed seeds and propagules under different management conditions.

Fire: For information on the use of prescribed fire to control this species, see Fire Management Considerations.

Cultural control: No information is available on this topic.

Physical or mechanical control: Some suggest that aggressive tillage or mowing may control thorny-olive [35], but others report that mechanical control of thorny-olive is slow and labor intensive [11]. These methods may not be appropriate for wildland management.

Biological control: As of 2011, no biological control agents had been tested or released for control of thorny-olive. There are few known thorny-olive pests in the United States [11].

Biological control of invasive species has a long history that indicates many factors must be considered before using biological controls. Refer to these sources: [55,58] and the Weed control methods handbook [51] for background information and important considerations for developing and implementing biological control programs.

Chemical control: The following references: [11,35,38] provide some guidelines for chemical control of thorny-olive. Byrd and Westbrooks [11] suggest that chemical control of thorny-olive can be slow, and signs of effectiveness may not be visible for "some time" after herbicide treatments. Herbicides are effective in gaining initial control of a new invasion or a severe infestation, but they are rarely a complete or long-term solution to weed management [10]. See the Weed control methods handbook [51] for considerations on the use of herbicides in natural areas and detailed information on specific chemicals. Integrated management: No information is available on this topic.

Elaeagnus pungens 10

Elaeagnus pungens is a species of flowering plant in the family Elaeagnaceae, known by the common namesthorny olive and silverthorn; also by the family name "oleaster". It is native to Asia, including China and Japan. It is present in the southeastern United States as an introduced species, a common landscaping and ornamental plant, and sometimes an invasive species.[1]

Contents

Description[edit source | edit]

E. pungens is a dense, branching shrub which can reach over 7 metres (23 ft) tall by 4 metres (13 ft) wide. It sprouts prolifically from its stem, spreading out and twining into adjacent vegetation. Parts of the stem are covered in thorns which can be up to 8 centimetres (3.1 in) long. The evergreen, alternately-arranged leaves are up to 10 centimetres (3.9 in) long but under 5 centimetres (2.0 in) wide. The undersides are silvery white with brown flecks. Tubular flowers are borne in clusters of up to three.[1] The flowers are yellowish or white and are sweet-scented.[2] The fruit is a drupe up to 1.5 centimetres (0.59 in) long which contains one seed.[1] It is reddish with silver scales.[2] Blooming occurs in the fall and fruit develops during the spring. The plant grows quickly, with shoots growing over one meter per season. The growth has been described as "aggressive", with shoots extending many meters into neighboring treetops. The seeds are dispersed by birds.[1]

Habitat[edit source | edit]

In China this plant occurs on hillsides and in thickets. In Japan it grows in scrub dominated by Quercus phillyraeoides and Pittosporum tobira. This plant was introduced to the United States from Asia in 1830. It has been used extensively as a landscaping plant. Its densely packed, spreading form has proved useful along roadsides and highway medians. It was also used to revegetate abandoned mining sites in Kentucky and other areas. It took hold easily and still persists in these places. It also spread into the wild, having escaped cultivation. In North Carolina it has been reported from longleaf pine forests, urban and maritime forests, and oak-hickory woodlands. In Alabama it grows in urban areas and in protected, natural habitats as a weed.

Cultivation[edit source | edit]

E. pungens as bonsai, Montreal Botanical Garden

Despite its invasive potential, E. pungens is widely cultivated as a garden plant in temperate regions. It tolerates varied environmental conditions, including heat, cold, wind, coastal conditions, shade, and full sun. It is very drought-tolerant. It can grow in varied soil types, including those found at mine spoils.[1] Numerous cultivars have been developed, especially for variegated foliage effects. Commercially available cultivars include 'Maculata', which has gold coloration on the leaves,[3] as well as 'Fruitlandii', 'Hosoba-Fukurin'[4] and 'Goldrim'.[5]

Ecology[edit source | edit]

Many birds feed on the fruits of the shrub. Birds are most attracted to the plants that produce the most fruit.[1] Studies have found that cedar waxwings attracted to roadside plantings of the shrub are susceptible to automobile-related mortality. In Brazos County, Texas between 8 March and 5 April 1981, researchers counted 298 cedar waxwings that had been killed while trying to get fruits from thorny-olive shrubs growing along one highway.[1]Wikimedia Commons has media related to: Elaeagnus pungens

References[edit source | edit]

  1. ^ abcdefgGucker, Corey L. (2011). Elaeagnus pungens. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. Retrieved 1 March 2012.
  2. ^ abElaeagnus pungens. Center for Aquatic and Invasive Plants, University of Florida IFAS. Retrieved 1 March 2012.
  3. ^E. pungens 'Maculata'. BBC Plant Finder. Retrieved 1 March 2012.
  4. ^E. pungens. NC State University. Retrieved 1 March 2012.
  5. ^"Elaeagnus pungens 'Goldrim'". Royal Horticultural Society. Retrieved 25 July 2013. 

Sources and Credits

  1. no rights reserved, uploaded by Alan Weakley
  2. (c) Kenpei, some rights reserved (CC BY-SA), https://upload.wikimedia.org/wikipedia/commons/1/12/Elaeagnus_pungens1.jpg
  3. (c) Kenpei, some rights reserved (CC BY-SA), https://upload.wikimedia.org/wikipedia/commons/f/f2/Elaeagnus_pungens5.jpg
  4. (c) Kenpei, some rights reserved (CC BY-SA), https://upload.wikimedia.org/wikipedia/commons/d/da/Elaeagnus_pungens2.jpg
  5. (c) Kenpei, some rights reserved (CC BY-SA), https://upload.wikimedia.org/wikipedia/commons/6/6d/Elaeagnus_pungens3.jpg
  6. (c) Kenpei, some rights reserved (CC BY-SA), https://upload.wikimedia.org/wikipedia/commons/6/6a/Elaeagnus_pungens4.jpg
  7. (c) omniscient_snail_sam, some rights reserved (CC BY-NC)
  8. Public Domain, http://eol.org/data_objects/24635877
  9. Public Domain, http://eol.org/data_objects/24635890
  10. (c) Unknown, some rights reserved (CC BY-SA), http://eol.org/data_objects/25451252

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