Family: Quassia Family (Simaroubaceae)
Origin and Distribution: This native of China was brought to North America in the 1700's as an ornamental tree. It escaped cultivation and became naturalized across much of the U.S. In Ohio, it is most abundant in the southern counties although it can be found throughout the state. Tree-of-heaven adapted well to city life, where large numbers were planted along streets and many more spread to vacant lots and waste areas. It thrives in the most inhospitable sites such as in alleyways, wedged between walls, along foundations, in cracks, and among rubble. It can be found growing in virtually any soil type but rarely in natural habitats or shade.
Plant Description: This perennial tree grows fast, although its life is relatively short (25 to 30 years). It is best described as persistent and tolerant. Tree-of-heaven produces 3-foot-long compound leaves that have many 3- to 5-inch-long leaflets. When crushed, leaflets emit a foul odor. In winter after leaves are shed, branches display distinctive leaf scars that are large and arranged in a U-shape. The small greenish flowers produce distinctive winged fruits with a single seed located in the middle. Plants reproduce by seeds and root sprouts, which can grow so fast and be so numerous that they quickly form a thicket.
- Root system - The root system should be regarded as extremely persistent and able to sprout shoots even under seemingly fatal conditions.
- Seedlings & Shoots - Young twigs are smooth and yellow-brown.
- Stems - Trees have been known to grow 100 feet tall (although rarely) and 3 feet wide. Trees develop a wide-spreading, rounded form when growing in the open and a single-stemmed, high branching form when crowded as in the city. Bark is usually thin, relatively smooth, and dark gray. In winter, branches display distinctive leaf scars that are large and arranged in a U-shaped pattern.
- Leaves - Leaves are alternate (1 leaf per node), compound, and can grow to nearly 3 feet long. Each leaf consists of between 11 to 41 leaflets that are 3 to 5 inches long and less than 2 inches wide. Leaflets are lance-shaped, dark green above, pale green beneath, and have a smooth edge except for 1 or 2 teeth near the base. Small oil-bearing glands at the base of leaflets emit an unpleasant odor when crushed described as resembling that of peanut butter or popcorn.
- Flowers - Small greenish flowers are produced in long, upright clusters at the end of new shoots. Male and female flowers occur on different plants. Pollen of the male flowers has a disagreeable odor.
- Fruits & Seeds - Winged fruits are between 1 to 2 inches long, red-brown, and have a slight twist on top. Fruits are clustered at the ends of branches. A single seed is located in the middle of each fruit.
Similar Species: Staghorn sumac (Rhus typhina) has similar compound leaves but its leaflets have toothed edges and its fruit is red and in cone-shaped clusters. Poison sumac (Rhus vernix) also has compound leaves and its leaflets have smooth edges, but poison sumac has white berry-like fruits while tree-of-heaven fruits are red-brown and winged.
Biology: Leaves appear late in spring, and leaflets turn yellow and fall off quickly following the first frost. Flowering begins in June and fruits that forms in October remain on the tree over winter. Stems can grow as much as 3 feet a year and will form thickets that crowd out native flora. The wood is soft. Roots may cause damage to drains, sidewalks, and foundations. However, the tree is resistant to city smog and pollution and may grow where few other trees can. Therefore, tree-of-heaven may be useful where a quickly growing shade tree is needed and its drawbacks can be tolerated. If cut, shoots sprout from stumps that can grow as tall as 9 feet in one year making the tree especially troublesome to control. Shoots must be repeatedly removed or herbicide brushed on the freshly cut stump to kill the tree.
Toxicity: Some people experience allergy to tree-of-heaven pollen. A few cases of contact dermatitus in humans that were exposed to the leaves or flowers have been reported. The reaction appears similar to poison ivy rash. It is suspected that roots as well as above-ground growth of Tree-of-heaven can cause gastroenteritis.
Facts and Folklore:
- The common name is thought to refer to the great height that this fast growing tree has the potential to reach.
- 'Ailanthus' was derived from the Moluccan 'ailanto' meaning 'tree that can grow up to the sky'.
- This is the tree referred to as 'the tree that grows in Brooklyn'.