I like to call Ailanthus altissima the tree of good or evil. Depending on your perspective, it is either the “ghetto palm,” an invasive pest, or the “tree of heaven,” a tough, hardy street tree once planted for its beauty.
Introduced into the United States from China in 1748, it was being planted as a street tree by the 1820s. Pollution-resistant, salt-tolerant, quick-growing, and with tropical-like foliage, what was not to love about this tree?
Peter Del Tredici, senior research scientist at the Arnold Arboretum, held a tree mob on July 22 on a specimen of this tree (accession #695-80-B). Before eventually turning brown, most ailanthus trees have fruit that go from green to yellow. The tree that Del Tredici collected goes from green to red, hence the form “erythrocarpa,” which means red fruit. Del Tredici described the red on the tree as a spontaneous mutaton that appears sporadically.
Del Tredici came upon this tree while driving near the intersection of I-95 and I-90, along the Charles River. The tree was hard to miss because, like most ailanthus, the trees sucker, leaving a clump of clones with the same characteristics.
The leaves of Ailanthus can easily be confused with those of sumac. Del Tredici pointed out a couple of differences. For one, the leaflets attach to their petioles lopsided. The big give-away, though, is the tiny gland at the tip of the small lobes near each leaflet’s base.
Del Tredici said this gland is an extra-floral nectary, where a plant produces sugar water to attract non-pollinating insects. Ailanthus may attract ants, which drive leaf-eating insects away. Del Tredici has not observed this behavior himself, but suspects that the glands are most active in the spring.
So why all the hate? Well, the tree is difficult to contain. It produces suckers all along its root system. Cutting down the tree only encourages the suckers, which grow at a rate so quick that other trees are hard-pressed to compete.
Ailanthus is also allelopathic, meaning it produces chemicals that inhibit the growth of other plants. In an article entitled Allelopathy and the Secret Life of Ailanthus altissima appearing in the fall 1997 issue of Arnoldia, Rod Heisey reports that the tree releases toxic ailanthone through its roots, although it is not known how effective this chemical is in soil with bacteria that can break down the compound, or if growth inhibition is the chemical’s primary purpose.
Pollen from Ailanthus flowers smells terrible. Del Tredici said that when that pollen fell into New York’s well-water, spoiling its taste, an uproar ensued.
Del Tredici said Ailanthus is still used as a street tree in Beijing. It is planted in tree pits so it cannot spread by suckering, and harvested for medicinal use, which helps keep down the tree’s population. The tree presumably also has many natural predators there. Despite the tree’s uses, Del Tredici said, a Chinese child who is a good-for-nothing ingrate is called a worthless Ailanthus root sucker.
Thus far, the tree has grown in the United States unchecked by pests. That may be changing. Del Tredici said that a verticillium fungus has been discovered in Pennsylvania that has killed more than 10,000 Ailanthus trees. The fungus has been isolated, but Del Tredici does not know of any instances where this verticillium wilt has intentionally been used to kill trees.
Along with many other states, Massachusetts has declared Ailanthus invasive, forbidding “importation, propagation, purchase and sale.” Del Tredici feels that existing plants in urban areas need not be targeted because they provide ecological services in places where other trees would not survive.
Native to China, Ailanthus has been used as a symbol of immigration. Del Tredici read us excerpts from the writings of Andrew Jackson Downing, which show the country’s changing attitudes toward the tree and toward immigrants.
At first, Downing waxed poetic in Treatise on the Theory and Practice of Landscape Gardening (1844 edition):
Ailanto is the name of this tree in the Moluccas, and is said to signify Tree of Heaven; an appellation probably bestowed on account of the rapidity of its growth, and the great height which it reaches in the East Indies, its native country. When quite young it is not unlike a sumac in appearance; but the extreme rapidity of its growth, and the great size of its pinnated leaves, four or five feet long, soon distinguish it from that shrub. During the first half dozen years it outstrips almost any other deciduous tree in vigour of growth, and we have measured leading stems which had grown twelve or fifteen feet in a single season. In four or five years, therefore, it forms quite a bulky head, but after that period it advances more slowly, and in 20 years would probably be overtopped by the poplar, the plane, or any other fast growing tree. There are, as yet, no specimens in this country more than 70 feet high; but the trunk shoots up in a fine column, and the head is massy and irregular in outline. In this country it is planted purely for ornament; but we learn that in Europe its wood has been applied to cabinet-work; for which, from its close grain, and bright satin-like lustre, it is well adapted. The male and female flowers are borne on separate trees, and both sexes are now common, especially in New-York. The male forms the finer ornamental tree, the female being rather low, and spreading in its head.
In New-York and Philadelphia, the Ailantus is more generally known by the name of the Celestial tree, and is much planted in the streets and public squares. For such situations it is admirably adapted, as it will insinuate its strong roots into the most meagre and barren soil, where few other trees will grow, and soon produce an abundance of foliage and fine shade. It appears also to be perfectly free from insects; and the leaves instead of dropping slowly, and for a long time, fall off almost immediately when frost commences.
The Ailantus is well adapted to produce a good effect on the lawn, either singly or grouped; as its fine long foliage catches the light well, and contrasts strikingly with that of the round-leaved trees. It has a troublesome habit of producing suckers, however, which must exclude it from every place but a heavy sward where the surface of the ground is never stirred by cultivation.
The branches of this tree are entirely destitute of the small spray so common on most forest trees, and have a singularly naked look in winter, well calculated to fix the attention of the spectator at that dreary season.
The largest Ailantus trees in America are growing in Rhode-Island, where it was introduced from China, under the name of the Tillou tree. It has since been rapidly propagated by suckers and is now one of the commonest ornamental trees sold in the nurseries. The finest trees, however, are those raised from seed.
Then, conveniently forgetting that he himself had advocated the planting of this tree, he rants against it, using racist overtones. Here’s an excerpt from “Shade-Trees in Cities” from his book Rural Essays published in 1852:
“Down with the ailanthus!” is the cry we hear on all sides, town and country, — now that this “tree of heaven” (as the catalogues used alluringly to call it) has penetrated all parts of the Union, and begins to show its true character. Down with the ailanthus! “Its blossoms smell so disagreeably that my family are made ill by it,” says an old resident on one of the squares in New-York where it is the only shade for fifty contiguous houses. “We must positively go to Newport, papa, to escape these horrible ailanthuses,” exclaim numberless young ladies, who find that even their best Jean Maria Farina, affords no permanent relief, since their front parlors have become so celestially embowered. “The vile tree comes up all over my garden,” say fifty owners of suburban lots who have foolishly been tempted into bordering the outside of their “yards” with it — having been told that it grows so “surprising fast.” “It has ruined my lawn for fifty feet all round each tree,” say the country gentlemen, who seduced by the oriental beauty of its foliage, have also been busy for years dotting it in open places, here and there, in their pleasure-grounds. In some of the cities southward, the authorities, taking the matter more seriously, have voted the entire downfall of the whole species, and the Herods who wield the besom of sylvan destruction, have probably made a clean sweep of the first born of celestials, in more towns than one south of Mason and Dixon’s line this season.
Although we think there is picturesqueness in the free and luxuriant foliage of the ailanthus, we shall see its downfall without a word to save it. We look upon it as an usurper in rather bad odor at home, which has come over to this land of liberty, under the garb of utility, to make foul the air, with its pestilent breath, and devour the soil, with its intermeddling roots — a tree that has the fair outside and the treacherous heart of the Asiatics, and that has played us so many tricks, that we find we have caught a Tartar which it requires something more than a Chinese wall to confine within limits.
Down with the ailanthus! therefore, we cry with the populace. But we have reasons beside theirs, and now that the favorite has fallen out of favor with the sovereigns, we may take the opportunity to preach a funeral sermon over its remains, that shall not, like so many funeral sermons, be a bath of oblivion-waters to wash out all memory of its vices, For if the Tartar is not laid violent hands upon, and kept under close watch, even after the spirit has gone out of the old trunk, and the coroner is satisfied that he has come to a violent end — lo, we shall have him upon us tenfold in the shape of suckers innumerable — little Tartars that will beget a new dynasty, and overrun our grounds and gardens again, without mercy.
The vices of the ailanthus — the incurable vices of the by-gone favorite — then, are twofold. In the first place, it smells horribly, both in leaf and flower — and instead of sweetening and purifying the air, fills it with a heavy, sickening odor; in the second place, it suckers abominably, and thereby overruns, appropriates, and reduces to beggary, all the soil of every open piece of ground where it is planted. These are the mortifications which every body feels sooner or later, who has been seduced by the luxuriant outstretched welcome of its smooth round arms, and the waving and beckoning of its graceful plumes, into giving it a place in their home circle. For a few years, while the tree is growing, it has, to be sure, a fair and specious look. You feel almost, as you look at its round trunk shooting up as straight, and almost as fast as a rocket, crowned by such a luxuriant tuft of verdure, that you have got a young palm-tree before your door, that can whisper tales to you in the evening of that “Flowery Country” from whence you have borrowed it, and you swear to stand by it against all slanderous aspersions. But alas! you are greener in your experience than the Tartar in his leaves. A few years pass by; the sapling becomes a tree — its blossoms fill the air with something that looks like curry-powder, and smells like the plague. You shut down the windows to keep out the unbalmy June air, if you live in town, and invariably give a wide berth to the heavenly avenue, if you belong to the country.
But we confess openly, that our crowning objection to this petted Chinaman or Tartar, who has played us so falsely, is a patriotic objection. It is that he has drawn away our attention from our own more noble native American trees, to waste it on this miserable pigtail of an Indiaman. What should we think of the Italians, if they should forswear their own orange-trees and figs, pomegranates and citrons, and plant their streets and gardens with the poison sumac-tree of our swamps? And what must a European arboriculturist think, who travels in America, delighted and astonished at the beauty of our varied and exhaustless forests — the richest in the temperate zone, to see that we neither value nor plant them, but fill our lawns and avenues with the cast-off nuisances of the gardens of Asia and Europe!
In 1943, almost a hundred years later, in her novel A Tree Grows in Brooklyn, Betty Smith also used Ailanthus as a symbol for immigration. Unlike Downing, she sees in the tree a positive symbol, tying it to the struggles of poor immigrants:
The one tree in Francie’s yard was neither a pine nor a hemlock. It had pointed leaves which grew along green switches which radiated from the bough and made a tree which looked like a lot of opened green umbrellas. Some people called it the Tree of Heaven. No matter where its seed fell, it made a tree which struggled to reach the sky. It grew in boarded-up lots and out of neglected rubbish heaps and it was the only tree that grew out of cement. It grew lushly, but only in the tenement districts.”
Look at that tree growing out of that grating. It gets no sun, and water only when it rains. It’s growing out of sour earth. And it’s strong because its hard struggle to live is making it strong. My children will be strong that way.
So tree of good or tree of evil? While Downing’s racism deserves condemnation, he is not alone in despising this tree. Ailanthus continues to damage our native ecosystems. Yet, I agree with Del Tredici that it does not make sense to eradicate the tree from areas in the city that would otherwise not support our native flora.