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| PHOTOS DONE AND ADDED TO THE TEXTE: SHAHRZAD GHAFFARI , Montreal, July 01.2011 Story of the tree to follow |
Informations de la site:
http://www.columbia.edu/itc/cerc/danoff-burg/invasion_bio/inv_spp_summ/Elaeagnus_angustifolia.htm
http://www.columbia.edu/itc/cerc/danoff-burg/invasion_bio/inv_spp_summ/Elaeagnus_angustifolia.htm
Common Name: Russian olive (also Russian-olive, Russian olive); Oleaster
Scientific Name: Elaeagnus angustifolia L.
Classification:
Division: Magnoliophyta (angiosperms, flowering plants)Class: Magnoliopsida (dicotyledons) Order: RhamnalesFamily: Elaeagnaceae (Oleaster family)
Identification: The Russian olive is a large, spiny, perennial deciduous shrub or small growing tree (up to 40ft.) that is usually found in riparian areas, as well as fields and other open areas. The plant has elliptical to lanceolate shaped leaves and thorny branches. The leaves are alternate and simple, about 1 to 3 inches long and ½ inch wide, distinctly scaly on the top and silvery and scaly on the bottom. The leaves of the Russian olive are dull green to gray in color. Buds are quite small, round and silvery-brown in color and covered with many scales. The branches are silvery, scaly and thorny when the plant is young, and turn a shiny, light brown color when mature. The bark on the Russian olive is at first smooth and gray, and then becomes unevenly rigid and wrinkled later on. Its fruit is like a berry, about ½ inch long, and is yellow when young (turning red when mature), dry and mealy, but sweet and edible. The fruit matures from August to October and stays on the tree throughout the winter. In mid-summer, from May to June, the Russian olive blooms fragrant yellow flowers with silvery-gray willow-like leaves, which can cause it to be easily confused with the willow-leaf pear tree.
Site and Date of Introduction: The Russian olive was introduced to the central and western United States in the late 1800’s as an ornamental tree and a windbreak, before spreading into the wild. By the mid 1920’s it became naturalized in Nevada and Utah, and in Colorado in the 1950’s.
Current Distribution: The Russian olive is found throughout North America, but mainly in the central and western portions of the United States. After introduction it escaped cultivation and naturalized in 17 western states from the Dakotas, Nebraska, Kansas, Oklahoma, and Texas westward to the Pacific coast. It is most abundant in the Great Basin Desert region and the riparian zones of the Great Plains. The Russian olive is also found on the east coast of the United States from Pennsylvania to Virginia, and in southern Canada, from Ontario to British Columbia.
Mode(s) of Introduction: The Russian olive was purposely introduced by human beings since it is an attractive, thriving landscape species. Its dense, silvery foliage provides a good hedge or screen to block out unwanted views. The plant is quite hardy and grows well near highways in particular. In the 1940’s, the Russian olive was deliberately planted in the eastern and southern U.S. for revegetation of disturbed areas and until recently it was transplanted for wildlife planting and windbreaks by the U.S. Soil Conservation Service.
Reason(s) why it has Become Established: The Russian olive has been extremely successful in the United States mainly due to its resistance to varying water, soil and temperature conditions, a proliferation of seed-dispersing birds and its nitrogen-fixing ability. Birds foraging on the Russian olive’s fruit scatter seeds at a very rapid rate. As the seeds are ingested along with the fruit by birds and other small mammals, they are subsequently scattered in their droppings. The seeds of the Russian olive are very resilient, enduring the stomach’s digestive juices, and distributing themselves for up to three years over a broad range of soil types.
The Russian olive is simply a very adaptive tree and tends to be an initial colonizer post-disturbance. It is very widespread in riparian zones and is found growing along floodplains, riverbanks, streams and marshes. The Russian olive can tolerate large amounts of salinity and can grow well in a variety of soil combinations from sand to heavy clay. It can also survive a unique range of temperature (from –50 to 115 degrees Fahrenheit) and can tolerate shade well, allowing it to withstand competition from other trees and shrubs. The Russian olive can also absorb nitrogen into its roots, thereby having the ability to grow on bare, mineral surfaces and dominate other riparian vegetation where old growth trees once survived.
ecological role in birds’ habitat, ecologists have found that bird species richness is actually greater in areas with a higher concentration of native vegetation. Over 50 different species of mammals and birds do eat the fruit, 12 of them being game birds. Deer and other livestock feast on the leaves of the Russian olive and beavers use the branches for constructing dams. The canopy of the Russian olive provides good thermal cover for some wildlife species. Doves, mocking birds, roadrunners and other birds use the thick growth of branches as nesting sites.
Ecological Role: The fruit of the Russian olive tree is a great source of food and nutrients for birds, so while this suggests the plant plays an important
Benefit(s): The Russian olive is principally an ornamental. Including the ecological benefits listed above, the Russian olive and its tremendous adaptability has allowed it to be planted for erosion control and highway and landscape enhancement. The branches from the Russian olive not only provide shade and shelter, but some fuel wood, gum and resin. The fruit of the Russian olive can be used as a base in some fruit beverages and the plant has also been know to be a source of honey. As previously mentioned, the Russian olives’ nitrogen-fixing ability makes it a good companion tree by increasing surrounding crops’ yield and growth, however with its ability to take over very quickly, it is wise to plant another species.
