Autumn olive (Elaeagnus umbellata) is a nitrogen-fixing shrub or small tree native to East Asia. It was introduced into North America in the 1830s. It grows rapidly and can reach a height of 20 feet. It has dark green, alternate leaves that are oval to lance shaped with smooth, wavy margins.
When the plant is 2 to 3 years old, it produces yellow flowers in April and May. The fruit is small, reddish pink and is readily consumed by birds and some small mammals. Each plant can produce several pounds of fruit.
Effects on Natural Communities
Autumn olive grows rapidly, thrives in poor soil, and its fruit is widely dispersed by birds. Due to its nitrogen-fixing capabilities, it can adversely affect the nitrogen cycle of the native communities that depend on infertile soils. These characteristics make it an aggressive and competitive threat to native species in open communities such as prairies, savannahs and woodlands.
Treating Autumn Olive in High-Quality Natural Communities
Young seedlings and sprouts can be hand pulled in early spring when adequate ground moisture is present to allow removal of the entire root system along with above-ground growth. Autumn olive is easily seen in early spring because its leaves appear while most native vegetation is still dormant.
A combination of mechanical and chemical treatment appears to be the most successful.
Cutting the plant off at the main stem at ground level and applying herbicide to the entire cambium layer of the cut stump has been effective in killing root systems and preventing re-sprouting.
- Herbicides recommended include glyphosate, triclopyr and picloram.
- Roundup herbicide (a formulation of glyphosate) has been effective in controlling autumn olive when used as a 10- to 20-percent solution and applied directly to the cut stump as described above. Although the Roundup label specifies a higher concentration for cut-stump application (50 to 100 percent), this lower concentration has proven effective. Roundup can be applied either by spraying individual stumps with a low pressure hand-held sprayer or else by wiping each stump using a sponge applicator (sponge-type paint applicators can be used).
With cut-stump treatment, herbicide is applied specifically to the target plant, reducing the possibilities of damaging nearby, desirable vegetation.
- Cut-stump treatment is particularly effective late in the growing season (July–September), but is also effective during the dormant season.
- Treatment of cut stumps should be done as soon as possible after cutting, i.e., within a few minutes.
- Glyphosate is a nonselective herbicide, so care should be taken to avoid contacting non-target species.
- Time of treatment should be planned so that glyphosate is not applied when rain is forecast within 6 to 8 hours.
- By law, herbicides may only be applied according to label directions.
Treating Autumn Olive in Other Than High-Quality Natural Areas
Same treatments as described for high-quality natural communities above. In addition, the following treatments are effective.
- Thin-line basal bark treatments with triclopyr herbicide (trade name Garlon) have demonstrated 95-percent kill. Undiluted Garlon 4 (or Garlon 4 diluted 50:50 with diesel fuel) should be applied in a thin, pencil-point line around the base of the plant 6 to 12 inches (15 to 30 cm.) above the ground. Application can be made with a handheld plant sprayer and should be performed during the dormant season to minimize risk to non-target species. A narrow band of Garlon 4 encircling the stem is needed to be effective.
- This method should not be used in high-quality natural areas and great care should be exercised to avoid getting any of the mixtures on the ground near the target plant since some non-target species may be harmed. Avoid using Triclopyr if rain is forecast for the following one to four days; otherwise runoff can harm non-target species.
- Foliar application of dicamba herbicides (available under a variety of trade names, including Banvel) and 2,4-D herbicides (available under a variety of brand names, including Crossbow) can provide total kill with little or no regrowth the following year. Banvel is mixed at the rate of 1 ounce per gallon of water plus 1/2 ounce of surfactant. The 2,4-D herbicide should be mixed according to label instructions. One hundred percent coverage of foliage should be achieved during the growing season (April–September). Therefore, this control application can be done any time during the growing season: summer application (July–August) is especially effective. Dicamba and 2,4-D are selective against broadleaf plants, so care must be taken to avoid contacting desirable, broadleaf vegetation. Do not spray so heavily that herbicide drips off the target species. Foliar spray of herbicides should only be used in less sensitive areas because of problems with contacting non-target species. The herbicide should be applied while backing away from treated areas to avoid walking through the wet herbicide.
- Although glyphosate (Roundup) is an effective foliar spray when applied during the growing season, it is not recommended because it is nonselective. Use of this herbicide as a foliar spray can result in unnecessary damage to non-target species.
Failed or Ineffective Practices
- Repeated pruning or mowing of established plants to ground level without subsequent herbicide application is not effective for autumn olive control. Each regrowth results in a thicker stem base and denser branches.
- Prescribed burning has not proven effective in controlling established autumn olive.