The Russian olive is a small deciduous tree or thorny shrub in the oleaster family. It can reach a height of 15 to 30 feet and grows in a round shape. The stems, buds and leaves have a silvery to rusty colored covering of scales. The flowers appear in May and June and are simple, bell shaped and yellow. They are highly fragrant. Olive-like fruits are light green to yellow, hard and fleshy. Russian olive holds nitrogen in its root system, which is why it propagates so readily.
Place of Origin
The first known cultivation of Russian olive trees was in Europe in 1736. It is native to southern Europe and western Asia, from Kazakhstan to Turkey and Iran. Its natural habitats are open fields, stream banks, roadsides and urban areas. It grows well on sand and is adaptable to a variety of soil conditions. It was valued as an excellent tree for erosion control.
Introduction to the U.S.
The Russian olive tree was first introduced into the U.S. landscape in the late 1800s as an ornamental tree and a windbreak. It was soon naturalized into the wild and spread rapidly. Its habitat now includes all but 10 states. The fruit is carried by birds and dropped into new areas where the tree reproduces easily. The seedlings are shade tolerant and sprout on bare mineral substrates as well as topsoil.
The United States Department of Agriculture has declared the Russian olive tree to be an invasive species because it crowds out native plants. Its presence in an ecosystem interferes with the natural plant succession, specifically of cottonwood trees along river banks. The Russian olive tree also taxes natural water sources where the native species of cottonwood and willow trees would thrive.
The Russian olive tree has historically been promoted for its capability to support wildlife and birds with its abundant olive-like fruit. The USDA Natural Resources Conservation Service reports that "research has determined that benefits are not as great as those provided by native species." It has been found that wildlife and birds reproduce in greater numbers on trees and plants native to the area.
Several methods of eradicating the Russian olive tree are used to help reintroduce and support native tree and shrub species. Removing the top growth and suppressing its regrowth are most effective. Several herbicides kill this tree, but repeated applications over one to two years are necessary and the subsequent chemical pollution is an environmental problem.