First introduced into the Unites States in the 1830s, the autumn olive provides a source of food for birds and wildlife. Early settlers planted these shrubs to provide windbreaks and reclaim disturbed areas of soil. Often considered an invasive species, autumn olive shrubs grow into rounded shapes that merge and form dense thickets. Like other types of shrubs, autumn olives go through a series of growth stages to reach their mature height of between 20 and 30 feet tall.
While autumn olives can also spread through sucker formation, these plants produce numerous seeds that sprout into new shrubs. Plants often produce as many as 20,000 to 54,000 seeds each year. Birds and mammals spread these seeds to various locations, eating them and disposing of them far from the parent plants. Although the seeds may germinate without stratification, a period of cold temperatures can increase the rate of success. About two months of temperatures around 41 degrees Fahrenheit can help promote germination. Seeds germinate and begin to grow about eight weeks after planting.
Like many types of flowering and fruiting shrubs, autumn olives concentrate on producing leaves and stems for the first few years. In autumn olives, this preflowering stage lasts for about three years, during which time the shrubs leaf out in the spring and continue to grow new leaves and branches until cold temperatures cause them to go dormant for the winter.
Autumn olives reach their blossoming stage between three and five years of age. At this point, the shrub's height reaches between 4 and 8 feet tall. During this stage, small flowers form along the thorny branches in the springtime. These yellow blossoms emit a pleasant fragrance.
Fruit forms in the fall on maturing shrubs. After the flowers fade from the shrubs, small oval fruits begin to form in their place. These edible fruits mature through the summer to form small, oval berries in the fall. A mature specimen can produce about 30 lbs. of berries every year. These speckled berries contain the seeds that reproduce into new trees.
Undisturbed, autumn olive shrubs live for more than 20 years. A dying shrub appears healthy around the edges and dry around its interior, due to its ability to produce suckers. These young shoots continue to spread and produce new shrubs, long after the parent plant withers and dies.