Russian Olive is Elaeagnus augustifolia, Autumn Olive is Elaeagnus Umbellata. Russian olive tends to grow more like a tree but may bush like. Autumn olive is multistemed and bush like reaching 20 feet talls. Imagine multiflora rose on steriods. Grows thick and created a ground cover that nothing will grow under so as your old oaks and hickories die they get replaced with autumn olive then new oak and hickory sprouts don't grow, because of the complete shading of the ground under the thick shrubery.