Autumn Olive

Background

Autumn olive (Elaeagnus umbellata) is an ornamental shrub first introduced to North America in the mid-1800s. This shrub’s silvery foliage, showy flowers, and colorful berries made it popular in landscaping, though it was also planted extensively for a period of time in natural areas to provide erosion control, wind breaks, and wildlife food. The abundance of fruit, which is readily dispersed by birds, is central to the spread of this species. From the East Coast as far west as Nebraska, autumn olive is an aggressive invader of roadsides, pastures, abandoned agricultural land, forest edges, and other disturbed habitats.

Description

Size

Rapidly growing, often multistemmed, and can reach heights of up to 20 feet and spread 30 feet wide.

Flowers

Trumpet-shaped, white to pale yellow flowers bloom in spring. Each flower has four petals, and the ½-to-¾-inch blooms are arranged in clusters of four to six.

Fruit

Clusters of four to six bright red, occasionally orange/yellow, fruit form in late summer, each ½ inch or less in diameter, flecked with silvery scales. Later in the season they may darken slightly and appear browner. When opened, they reveal a single seed.

Leaves

Simple, elongate leaves with smooth, or entire, margins arranged alternately along the stem, each 2–4 inches long. The upper surface is pale green, while the underside appears silver or white due to the presence of small silvery scales.

Stems

All stems are ashy brown, but silvery scales are especially prominent on young stems, which sometimes appear totally gray. The stems also bear sharp, stout spines.

Look-alikes

The terms "autumn olive" and "Russian olive" are often used interchangeably, but Russian olive (Elaeagnus angustifolia) is actually a different species. It is an invasive tree that looks similar to autumn olive, but has some key differences. Russian olive can appear shrub-like when small, but it grows into a large tree form. The leaves of Russian olive are longer and narrower, and the leaves and twigs tend to droop, giving the tree a willow-like appearance. While Russian olive does exist in Pennsylvania, it is much more common in the western U.S., whereas autumn olive is much more common in the east. The species are ecologically very similar and require the same control treatment.

Dispersal

Autumn olive spreads through seed dispersal, primarily by birds. The fruit persist through fall before drying up and falling off the plant. Unlike many native shrub species, autumn olive matures quickly and can produce fruit in as few as three years. Though abundant, the fruit are of low nutritional value to wildlife in comparison to the native shrub species they displace.

Site

Intolerant of dense shade, autumn olive is most commonly found on disturbed sites with full to partial sun. However, it is highly tolerant of salinity, extreme pH, and heavy metals, traits that enable the plant to survive or thrive on very poor sites, including highway roadsides, mine spoils, and other postindustrial sites. This is partly due to autumn olive’s ability to create its own absorbable form of nitrogen, altering the local nitrogen cycle to which native plant communities are adapted. Historically this has been seen as a positive feature for mineland reclamation. However, this strategy gives it an edge in out-competing native plants

Management Calendar

The management calendar for autumn olive is quite flexible because the foliage emerges early and falls late. Basal bark and cut stump treatments provide a year-round window of opportunity

Herbicide Treatment and Timing

Autumn olive leafs out early and drops its leaves late, providing a long foliar herbicide application window. Basal bark and stump treatments can be made anytime the weather permits. Product names reflect the current Pennsylvania state herbicide contract; additional brands with the same active ingredients are available

Control

In a prescription to control autumn olive, plan to “save the best," or work from least to most invaded areas, such as areas where there is desirable native vegetation and few invasives. This will maximize cleared areas, not only producing an outcome of higher ecological value, but also creating a much greater sense of accomplishment, as autumn olive is difficult to eradicate once it is established.

As the seeds are dispersed by birds, new invasions can and will reoccur, but spot removal of a few isolated individuals is easily accomplished as a part of any invasive plant maintenance program.

Individual small plants can be pulled by hand or dug up. For larger plants or infestations, cutting can be a helpful first step in an herbicide approach, both to help with access and because resprouting stumps provide smaller, more manageable targets for herbicide applications. Smaller stems are easily cut with heavy-duty rotary or flail cutters (i.e., "bush hogs"). For larger stems, fixed-tooth, drum-type forestry cutters have the capacity to cut down large stems and also finely chop the debris.

For mowing to be effective, it must be followed with an herbicide application to cut surfaces or regrowing sprouts. Oil-based treatments (1:4 mixture) can be applied to the stumps anytime after cutting, while water-based (1:1 mixture) treatments should be applied as the stems are cut. Treating sprouts with a fall foliar herbicide application (or application the following growing season) is an alternative to treating cut stumps when immediate application of the herbicide to stumps is not practical. Selectively treating knee-to-waist-high resprouts with a backpack sprayer is a relatively quick process on low-growing foliage.

Foliar herbicide treatments with a backpack sprayer are the most effective means to treat sites with low to moderate plant densities. An effective herbicide for autumn olive is triclopyr, or a combination of glyphosate and triclopyr when targeting multiple species. Glyphosate alone is not effective as a foliar spray. Other herbicides proven effective for autumn olive are 2,4-D (in combination with triclopyr), imazapyr, and dicamba, all available under many different brand names. When using a new herbicide, be aware of its properties, such as soil activity and volatility. Be sure to calibrate your spray equipment to achieve the desired dosage, and follow the label.

Basal bark treatments are effective against autumn olive and can be applied throughout the year. Basal bark treatments use a concentrated mixture of the triclopyr ester formulation mixed in basal oil and applied to the entire circumference of the lower 12 to 18 inches of the intact stem, depending on its size. Pathfinder II is a ready-to-use triclopyr ester plus oil product that can also be used, no mixing required.

Human Use

Autumn olive is well established across the Mid-Atlantic due to its extensive intentional planting to provide wildlife food and revegetate mine spoils in the mid-1900s. While this shrub does produce huge amounts of berries eaten by birds and mammals and can thrive on reclaimed mine sites, where pH extremes and high levels of toxic heavy metals are common, these positives do not outweigh the negatives associated with this shrub’s ability to invade and take over natural areas. Like other invasive shrubs, autumn olive’s fruit is low in proteins and fats but high in carbohydrates, rendering it less nutritious than fruit from the native plants that it displaces from habitats. Additionally, the fruit of autumn olive is sometimes collected and eaten by humans, usually made into jellies or jams. Care should be taken when collecting for consumption since heavy metals can be translocated from the roots to other plant parts, including the fruit.

Prepared by Skylure Templeton, Art Gover, Dave Jackson, and Sarah Wurzbacher.