Nature Bulletin No. 563-A   April 19, 1975

Forest Preserve District of Cook County

George W. Dunne, President

Roland F. Eisenbeis, Supt. of Conservation



****:THE AILANTHUS: TREE OF HEAVEN



One of the depressing aspects of congested areas in a big city is the 

almost total absence of trees. Either they are poisoned or they are 

starved for food, water and light. Smoke and fumes, dust and grime, 

refuse and ashes, cinders and salt, make it impossible for our native 

trees to survive -- especially when the soil around them is covered with 

pavement or packed by trampling feet. But some people living in such 

neighborhoods, and instinctively yearning for a green growing tree, 

have found one kind that will thrive even under those conditions: the 

Ailanthus.



Over two centuries ago it was brought from China to Europe; and then 

in the early 1800's, to America. Ailanthus is the Latinized form of 

"ailanto," a native word of the East Indies, meaning Tree of Heaven -- a 

tree that overtops other trees. Its scientific name is Ailanthus altissima, 

the latter word meaning "very tall. " Its nearest relatives are eight or 

nine trees and shrubs of Asia and Australia. They belong to the Quassia 

family named after a tree of the New World tropics, whose wood is 

used in the drug industry.



Notable for its handsome foliage, the ailanthus is a rapidly growing tree 

that becomes rather large with a spreading crown of a few main 

branches and smooth striped bark. The wood is weak, soft and of little 

use. The twigs are coarse and have exceptionally large leaf scars with a 

prominent bud in a notch on the upper side. The leaves are alternate, 

very long, pinnately compound with from 13 to 25 leaflets each, and 

have a strong unpleasant odor when bruised.



Huge loose clusters of small greenish-yellow flowers appear in June or 

July, the male and female flowers being on separate trees. The male 

pollen-producing flowers have such a disagreeable powerful smell that 

male trees are seldom planted or allowed to grow. The mature female 

trees bear great masses of seeds that are very showy at first -- yellow 

tinged with crimson. Each seed has an inch-long twisted wing at either 

end. Months later, when brown and dry, they snap off in the wind and 

spin away like little airplane propellers.



One such tree can scatter seeds for blocks around and, because they 

seem to be able to germinate and grow almost anywhere, the ailanthus 

is like a weed. Seedlings pop up in lawns, gardens, hedges, around the 

foundations of buildings, in roof gutters, and even take root in crevices 

of brick or concrete walls. Not only that: around one of these prolific 

trees a thicket sprouts from its wide-spreading roots. If one is cut down 

without grubbing out the roots, it may grow again and, a year later, be 

ten feet tall.



The ailanthus has become naturalized and now grows wild around many 

big cities. It is remarkably free from diseases and insect pests. However, 

in the Orient its leaves are the preferred food of the ailanthus silk. moth, 

a near relative of the Cecropia, one of the largest of our native moths. It 

is raised to produce silk but is far different from the common 

domesticated silkworm which feeds on mulberry leaves. The silk 

unwound from its cocoons wears much better than that of the common 

silkworm but is not so soft and glossy. In China, a man's coat made of 

ailanthus silk may have been worn by his father and grandfather before 

him. Its commercial production was tried in France and, in 1861, in the 

United States but abandoned because of the excessive hand labor 

required.



In America, the ailanthus is the "Tree of Cities. "