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March 2010

Despite the Lycopene, Still a Bad Actor
Autumn Olive

Contact: Carole Bergmann, M-NCPPC | Carole.Bergmann@mncppc-mc.org

autumn-olive
Photo: Carole Bergmann, M-NCPPC

(scroll to bottom for more images)

ANNAPOLIS, MD (March 3, 2010) - Over the years, plants that have become invasive were once thought to be beneficial – kudzu and multifora rose are famous examples. Autumn-olive could be included in that group; it and its cousin, Russian-olive, were touted as trees that “grew fast, grew anywhere, and had few pest problems.” And now, many health and nutrition websites are singing the praises of the lycopene-rich fruits that autumn-olive bears and encouraging people to plant a tree or two in their gardens. This could make the growing problem of autumn-olive invasion even worse if birds, skunks, raccoons, opossums and other animals are offered additional opportunities to move the abundant fruits to meadow areas, forest edges and interiors, highway verges and medians throughout the mid-Atlantic. Lycopene is NOT an essential human nutrient and its antioxidant benefits remain unproven. Anyone who has seen a huge stand of autumn-olive—botanically classed as a large shrub or small tree—taking over an open field knows that this invasive can do considerable damage to watershed ecosystems. For these reasons, autumn-olive has been chosen as the MISC Invader of the Month for March 2010.

Autumn-olive (Elaeagnus umbellata Thunb.), which is not a true olive, was introduced to the United States in 1830 and widely planted for wildlife habitat, to create windbreaks, as an ornamental, and to restore deforested and degraded lands, especially from strip-mining. Since it can survive salt, pHs as low as 4.0, is drought tolerant, and grows in a variety of soil types and moisture regimes, it has the ability to invade a wide variety of habitats. Autumn-olive threatens native ecosystems by outcompeting and replacing native vegetation such as viburnums, spicebush, hollies, and dogwoods. The dense shade it creates can suppress the growth of early succession plants that require direct sunlight. Native plant succession and nutrient cycling can also be severely impacted by autumn-olive’s ability to fix nitrogen and alter soil chemistry. This is another reason why this invasive can thrive almost anywhere, even on bare mineral substrates. Some recent research looking at N-fixing species’ impact on water quality has indicated that the nitrogen load in stream systems can be impacted by nitrogen leaching into soil water and subsequently into groundwater.

Autumn-olive is a deciduous shrub or small tree that can grow to 20 feet. It can be multi-stemmed and shrublike in habit or appear as a small, single-trunked tree. One of the plant’s most distinctive features is the covering of silvery or rusty scales that appear as tiny dots on stems, buds, fruits and leaves. The silvery-white scales on the undersides of the ovate to lance-shaped leaves can cause a shimmering effect when a stand of autumn-olive is viewed from a distance in a light breeze. Leaves are smooth-margined and alternate along the stem. Small, aromatic, light yellow flowers appear usually in June or July followed by red or pinkish small, round, silvery scale-dotted fruits. Autumn-olive spreads by seed and re-sprouts vigorously when cut, mowed, or burned, often producing even thicker stems and denser branches. In comparison, Russian-olive (Elaeagnus angustifolia L.) - which is more common in the West, but often occupies the same habitats as autumn-olive in the East and Midwest — is distinguished by usually thorny branches, narrower leaves that are often more silvery in color, and by dry, mealy yellow fruits.

Autumn-olive is native to China, Korea and Japan. It occurs in the U. S. in all states east of the Mississippi River and in the Canadian province of Ontario. It has also been reported in several states west of the Mississippi and the Pacific Northwest. Autumn-olive is one of the earlier shrubs to break dormancy, putting out foliage as early as the beginning of March. Young plants grow rapidly, producing fruits in 3-5 years. Autumn-olives produce a large amount of seed, with each tree capable of producing tens of thousands of seeds per year. Research has also shown that autumn-olive seeds have a high germination rate.

The first and foremost control measure is: do not plant autumn-olive! Since burning and cutting stimulate resprouting, herbicide treatment may be the only effective way to eradicate large patches. One method of application is to cut the plant off at the main stem and apply concentrated herbicide on the stump. Treatment is especially effective late in the growing season, July through September, but is also possible during dormancy. Foliar applications may be adequate for small patches; the best time being late August through September when the plant is actively translocating materials to the roots. Contact your local forestry office or University of MD Extension office for specific recommendation and as always follow label directions.

Carole Bergmann and Paul Carlson contributed to this article.

For more information about this and other Invasive Species of Concern, visit www.mdinvasivesp.org

photos available electronically on request.

Norway maple fruit Norway Maple bark
Carole Bergmann, M-NCPPC
Carole Bergmann, M-NCPPC
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