Tree-of-Heaven

Tree-of-heaven (Ailanthus altissima (Mill.) Swingle) is a native of central Asia, which was introduced to the U.S. in the 1780’s as an ornamental plant.  Since that time it has become an invasive pest in our forests.

Tree-of-heaven impacts our native forests by forming dense thickets and replacing many of our native plants.  The dense thickets cast heavy shade that prevents native plants from becoming established and surviving.  Tree-of-heaven also deposits chemicals in the soil that impact the growth of competing plants (our native species).  In urban landscapes, tree-of-heaven develops an extensive root system that can damage infrastructure and create a nightmare for anyone trying to get rid of the tree.  Once the main stem is cut down, the tree sprouts prolifically from the roots.

Tree-of-heaven currently is known to be in 34 of Arkansas’ 75 counties.  It is not our most widespread invasive pest, but it is becoming more common in our landscape.

Tree-of-heaven is easy to identify.  Superficially the young trees resemble our sumacs, although it is not closely related.  The alternate pinnately compound leaves are 1 to 4 feet long and have 11 to 41 leaflets.  Each leaflet has two glandular teeth near the base but otherwise has smooth margins.  Bark of young twigs is olive green, turning gray with age.  Texture of the branches and stems is nearly smooth with abundant lenticels on younger stems and branches and low ridges and broad shallow fissures on older stems.  Twigs have large heart-shaped leaf scars and a tan pith.  Small yellowish-green flowers grow in long clusters at the ends of the branches in mid to late spring.  Male and female flowers are on separate trees.  The fruit is a distinctive samara with a seed in the middle.  Most of the samara is flat, but the end is usually twisted about 90 degrees.