At the beginning of the 20th century, Russian olive was introduced to North America as a tree that could serve as a windbreak, prevent erosion, and provide wildlife shelter. The California Department of Fish and Wildlife describes the deciduous species as native to Europe and Asia. Over time, however, the tree became an invasive plant in parts of the United States.
The tree’s ability to thrive in varied conditions helps explain its spread. Its seedlings can grow in full sun, under shade, or through heavy ground cover, while native cottonwoods and willows generally establish themselves in open, disturbed areas. Russian olive also tolerates saline and alkaline soils and can gain an advantage along regulated rivers, where reduced flooding may limit the growth of native trees. Along Washington’s Yakima River, thickets of Russian olive have replaced black cottonwoods and native willows in some areas. Subsequent growth produced dense thickets in which other riparian species could not survive. For those seeking a shade tree without introducing an invasive species, the California Department of Fish and Wildlife recommends considering valley oak. This native deciduous tree provides habitat for birds and other wildlife and can offer substantial summer shade.
Along the Milk River in Montana and Alberta, nearly 500 Russian olive seedlings and saplings were planted in the floodplain in 1950. Because it can grow up to 100 feet tall, however, it needs plenty of room.
Russian olive’s history shows how a tree introduced for useful purposes can become an ecological problem as it spreads beyond cultivation. Checking a species before planting it can help prevent future removal work and protect native vegetation.
