Not all of the nature you see around you is strictly natural. This Russian olive tree is an invader – an invasive species. Invasive species are animals, plants or insects that are non-native and detrimental to the ecology of the area. Many invasive plants are spread by accident, either by hitchhiking on peoples’ clothing or by the droppings of animals that have eaten the plant. However, there are numerous invasive plants that were purposely planted by well-meaning humans attempting to solve a problem.
The Russian olive tree (Elaeagnus angustifolia L.) is one such plant. Native to Europe and Asia, the Russian olive was brought to the United States in the early 1900s. It was used for windbreaks, erosion control, and ornament. The arid landscape of eastern Washington was a perfect home for the tree, and federal authorities encouraged ranchers and farmers to plant Russian olive trees to control erosion and benefit wildlife. It quickly established itself on the banks of rivers, lakes, and other waterways.
The Russian olive produces abundant fruits which many types of birds and mammals eat. Deer and cattle eat its leaves. Birds eat the seeds and make good use of the leafy canopy to build their nests. Beavers use the tree limbs to build dams. Humans can also make use of resin produced by the tree, and the fruit of the Russian olive can be used in the making of beverages.
Despite its benefits to some wildlife, the rapid spread of the Russian olive makes it a threat to other species of plants. It crowds out native species like willow and cedar. Its denseness and height, up to twenty-five feet tall, block out sunlight. A new theory also suggests that the tree can pollute water sources by increasing nitrogen levels, encouraging algae growth which kills off fish.
Many states now classify the Russian olive as a noxious weed and call for its eradication. It is a challenging tree to eradicate, however. In addition to spreading via seeds, it also spreads by sending out shoots from its roots. The most effective way to kill it seems to be a combination of cutting it and then chemically treating the area. In Montana, ranchers are being offered money to remove the Russian olive trees from their land and replace them with native trees.
If you look around, you might see other invasive plants. Palouse Falls is the adopted home of at least eleven invasive plants. A few of the most prolific are reed canary grass, poison hemlock, cheatgrass, knapeweed, and bulbous bluegrass. Make sure to check your shoes and clothes before you leave to help stop the spread of these alien invaders.