Three species of non-native trees are of concern in the Arkansas River valley because of their effect on native habitat.
Native to central Asia and Africa, tamarisk, also known as salt cedars, are shrubs or small trees that grow in thickets imported to North America as ornamental shrubs in the 1800s. Some varieties reach up to 50 feet high. One tree can use up to 200 gallons of water per day and produce up to 2.5 million seeds. They are exceptionally resistant to drought and fire and choke out native vegetation. They are controlled by a combination of chemical, biological and mechanical methods.
Native to China, eastern Siberia, and Korea, the Siberian elm produces thousands of seeds that quickly germinate, particularly in disturbed areas. The fast-growing tree was brought into the United States in the 1860s and has spread to most states. It can reach 50-70 feet in height. It grows well in dry conditions and quickly displaces native trees. They can be controlled chemically, manually and by burning seeds.
Native to southeastern Europe and western Asia, Russian olives are small thorny trees that out-compete native species. They first came to the country as ornamental trees, then escaped to the wild. They were formerly recommended for windbreaks. The tree thrives in poor soil. While offering some food and habitat for wildlife, Russian olive is less suitable than native plants. Mowing and removing dead vegetation may be the most effective control.