Introduction:
Autumn olive (Elaeagnus umbellata) Weed Bush.
Elaeagnus umbellata is valued as an ornamental because of its silvery foliage and flowers and its hardiness under dry conditions. It invades grasslands and disturbed areas adjacent to the plantings, and encroachment can be rapid because of its high seed production and germination rate. It grows well on a variety of soils, including sandy, loamy, and somewhat clayey textures. It does very well on infertile soils because its roots can fix nitrogen, which has also fostered its use as a nurse plant in walnut orchards. E. umbellata seeds are ingested with fruit and dispersed by birds and mammals. Seeds are also used in some places for wildlife plantings.E. umbellata has the potential of becoming one of the most troublesome adventive shrubs in the central and eastern United States.
Description:
E. umbellata is a deciduous, thorny shrub that attains a height of up to 3.5 metres. Thorns are about 2.6cm long, bearing a bunch of flowers and a cluster of leaves; bark is removable in longitudinal strips, exposing the white hardwood underneath. One important distinguishing characteristic of this plant is that its shoots and young branches are clothed with very attractive white, silvery scales that disappear with the commencement of rains. Leaves are lanceolate and alternate, variable in size, and have an average length and breadth of about 2.7 and 1.2cm respectively. They are silvery on the ventral surface and hairy on the dorsal surface in the beginning, then glabrous at maturity. Flowers are always in axillary clusters, bisexual, fragrant, stalked, white to light yellow, 8-9mm in length and 7mm in diameter. The perianth is densely scaled, four-lobed, and nearly companulate. The androecium comprises four very small stamens attached to the mouth of the corolla tube. The gynoecium is simple, has one pistil, and is 7mm long on average. Fruits are ovoid to globose, 3-9mm in length, and 5mm in diameter. The epicarp is thin, covers the whole fruit; the mesocarp is pulpy and juicy. The pedicel is 5 to 6mm long. Freshly picked fruits are coral pink. Seeds are 7-8mm in length, 2 to 3mm in diameter, and saffron yellow in colour.
Occurs in:
Natural forests, range/grasslands, ruderal/disturbed.
Habitat description:
Elaeagnus umbellata can grow well on a variety of soils, including sandy, loamy, and somewhat clayey textures with a pH range of 4.8-6.5. It
Autumn olive (Elaeagnus umbellata) Distribution in Central America shown in Green.
apparently does notgrow as well on very wet or dry sites, but it has been described as having excellent tolerance to drought. Mature trees tolerate light shade but produce more fruits in full sun, and seedlings may be shade intolerant. E. umbellata invades prairies and fields, and it also grows in forests in its native and alien ranges.
General impacts:
The nitrogen-fixing capabilities of E. umbellata has the capacity to adversely affect the nitrogen cycle of native communities that may depend on infertile soils.It exhibits prolific fruiting, rapid growth, is widely disseminated by birds, and can easily adapt to many sites. It is vigorous and competitive against native species. E. umbellata seems to be a problem only in locations where small stands or rows were planted, usually within the last 10-20 years, and have begun to spread into adjacent fields or natural areas. It apparently can become troublesome where it occurs on or next to prairies with infrequent prescribed burns because it resprouts quickly after fire damage or cutting. E. umbellata is just beginning to be recognized as a potentially serious problem exotic.E. umbellata has the potential of becoming one of the most troublesome, adventive shrubs in the central and eastern United States.
Geographical range:
Native range: Elaeagnus umbellata is native to China, Korea, and Japan.
Known introduced range: E. umbellata was introduced to the United States for cultivation in 1830. It occurs from Maine to New Jersey and Pennsylvania and west to Wisconsin, Illinois, and Missouri.It also occurs, but has not naturalized in, Hawai‘i, Nevada, New Mexico, Oregon, Texas, Utah, and Wyoming.Sources say that it occurs in India and Afghanistan but not as widespread.
Local dispersal methods:
Consumption/excretion:The seeds are ingested with fruit and are dispersed by birds and mammals.
Autumn olive (Elaeagnus umbellata) Weed Flower.
Management information:
Preventative measures: A Risk Assessment of Elaeagnus umbellata for Hawai‘i and other Pacific islands was prepared. The alien plant screening system is used with minor modifications for use in Pacific islands. The result is a score of 13 and a recommendation of: “Likely to cause significant ecological or economic harm in Hawai‘i and on other Pacific Islands as determined by a high WRA score, which is based on published sources describing species biology and behaviour in Hawai‘i and/or other parts of the world.”
Chemical: Since burning and cutting stimulate resprouting, herbicide treatment may be necessary to eradicate large patches of E. umbellata. One method of application is to cut the plant off at the main stem and paint the herbicide on the stump. Glyphosate is effective and commonly used. Foliar applications may be adequate for small patches; the recommended dilution of glyphosate in this case is a 1-2% solution. Dormant season basal applications (stem injections) of triclopyr alone or in combination with 2,4-D provided excellent control of autumn olive at very low concentrations (down to 1% triclopyr in diesel oil). The lowest concentrations of triclopyr and all treatments with the 2,4- D/triclopyr combinations provided slower kills than higher concentrations of triclopyr alone, but only one of the treatment plants were expected to survive. Dicamba applied with a surfactant provided 90% total kill and severely retarded the growth of surviving stems the following year.
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