Invasive Plant Profiles Part Three: Russian & Autumn Olive

Invasive plants can be introduced unknowingly, as landscape specimens, or as purposeful releases to theoretically benefit wildlife. Each of these modes figure into the spread of Autumn Olive (Elaeagnus umbellata) and its cousin Russian Olive (Elaeagnus angustifolia). Both plants arrived in North America in the mid- to late 1800s from the Orient and Western Asia.

Over the last 200 years, government agencies bent on improving diminishing game populations, have encouraged (and even funded) landowners and agencies to plant what were once considered to be great habitat or erosion control species, including invasive Autumn and Russian Olives. The irony of all this was, the same agencies who cost-shared for these plantings, later cost-shared to control or eliminate the very plants they introduced!

I was just as guilty when it comes to Autumn Olive. In my formal training, I was taught that Autumn Olive was a great wildlife plant in the eastern U.S., providing both food and cover for game and non-game birds. They grew fast and began making abundant fruit by three years of age; producing several pounds of seed-filled fruit per plant. Its fruits are highly prized by birds, the primary distributors of new plants. You will find shrubs or small trees as high as 20 feet along fence edges and within forest stands frequented by birds. Once established, the plants begin the process of capturing the site, effectively eliminating native plant diversity.

There is a western counterpart to Autumn Olive: Russian Olive. In both species, the plants are very attractive, with silvery leaves either on the underside (Autumn Olive) or the top of the lead (Russian Olive). It is easy to recognize why they became so popular as a landscape species. However, the stems and twigs can be armed with sharp thorns, which can be quite a surprise if you do not expect them. One of the most interesting things about both species is their ability to thrive in a variety of soils and droughty conditions. And both are even capable of fixing nitrogen in the process. In essence, they create their own beneficial habitats. These were “sales points” offered in the wildlife habitat management guides in the 1950s. These also are traits making Autumn and Russian Olive strong competitors, which has a negative effect on natural succession of forests and brushlands.

Normally, areas are cleared by natural events such as ice storms, tornadoes and wildfires, which start the process of secondary succession. Pioneer species such as annual grasses and weeds quickly move into the site by way of highly mobile seeds, providing a protective cover to eroded, mineralized soil. As these plants develop, they improve the site for less competitive species such as perennial herbaceous plants, woody shrubs and various trees. In nature, as plant communities grow upward, bottom layer species are displaced through shading. Eventually the site succeeds to forest species and diversity increases over time. Some understory species exist where sunlight reaches the forest floor. Each distinct stage of succession carries with it specific species of animals adapted to that specific point in time.

If, on the other hand, exotic plants enter this natural process, they tend to capture the site during early succession. As a result, a habitat with lower diversity ultimately emerges. We have a saying in wildlife biology: “Diversity breeds stability!” The more diverse a plant community, the greater the diversity of animal species. When plant communities lose diversity, numbers of vertebrate species decline. Hence, an area dominated by exotic species such as Autumn and Russian Olive, although producing a lot of seasonally available food, are extremely damaging to wildlife populations.

CONTROL AND MANAGEMENT

My personal experience has mostly been with Autumn Olive in the Lake States, particularly Michigan. We have battled these plants around the Turtle Lake Club, since my arrival in 2003. Turtle Lake managers Wayne and Luke Sitton were dealing with these pests long before that. We experimented with Autumn Olive at the Institute for White-tailed Deer Management and Research here in East Texas back in the 1970s, but fortunately we recognized its potential problems and have virtually eliminated the species since then. Once established, as with the other invasive plants, it is almost impossible to manage them, much less eradicate them from wildlife habitat. Although the goal should be to not allow exotic species to become established, this is rarely an option in wildlife management. Exotics seem to not be noticed until they become a significant problem; then the “war” begins!

The first step in dealing with invasives is to establish the distribution of plants on your property; or, in the case of resource management agencies, their distribution over the landscape. Modern mapping techniques such as Geographic Information Systems (GIS) certainly have been helpful in this regard. Yet, it takes a lot of time and money to do this type of work, two things many landowners or agencies do not have. Once Autumn and/or Russian Olive has been located on your property, however, you can formulate a proactive management program, involving several control agents described below.

First, I am not aware of any effective biological control agent for either species of Olive. So, that is out of the picture entirely. High intensity grazing by livestock is not feasible, because woodland grazing is no longer popular, and livestock often prefer beneficial species over the exotics. We have investigated prescribed burning, but the results often are patchy due to heavy stocking of plants producing shade and reducing fuel. Where we do get a reasonably good burn, we just kill back the plants, which in turn sprout quickly, requiring a perpetual series of controlled burns.

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Mechanical control often does more harm than good, since it disturbs the plant community, reducing species diversity. Grubbing, raking and disking are labor intensive and the cost per acre can be quite high. In small areas, you can dig out the larger plants, making sure to pull up the roots or the plants will just re-sprout. The best solution for dealing with invasive Olives is herbicides. Two of these — glyphosate and triclopyr — again emerge as “go-to” chemicals. Glyphosate can be sprayed over small plants, while Triclopyr is excellent for basal spraying and foliar application. We really like Triclopyr, in a mix with either mineral oil or diesel (check recommended proportions in your area).

Individual plant application is the most ecologically sound method for killing vegetation, but it can be expensive. The Pennsylvania State University Extension Service developed a helpful table (see graphic) for making decisions about chemical control. Timing always is critical when applying herbicides. When using the PSU time-table, be aware that they are making recommendations for a colder climate than further south, so you will have to adjust timing accordingly. You want actively growing vegetation at time of application.

IN CONCLUSION

Again, the take-home lesson is not to get into trouble in the first place! New and exciting plants touted in the popular press may seem magical, but once the genie is out of the bottle, it is hard to put it back. That is why I have been involved in native plant breeding for several years at Stephen F. Austin State University, in cooperation with other universities and scientists. Our position is that we will improve what grows natively, when possible, and avoid problems for future biologists, managers and landowners.