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Brushpiles: Tree of Heaven

Posted: July 7, 2014

Brushpiles is the opinion page of Forest Leaves. It’s a place for you to write in and share your reactions and thoughts about recent articles in the newsletter. This Tree of Heaven piece was written by Bill Paxton in response to his concerns about efforts to eradicate Tree of Heaven.

I was giving a talk in my Penn State speech class about my butterfly and moth collection. Afterwards, a very attractive architectural student asked if I had a Cynthia moth, since her name was Cynthia. I showed her the adult Ailanthus silk moth (Samia cynthia) and a lasting relationship was launched.

This prize of lepidopterists has a caterpillar that feeds only on Ailanthus altissima, which is Tree of Heaven. It comes from China and was established in the Philadelphia area in the 1860s. I will quote directly from Our Native Trees by Harriett L. Keeler, published in 1910 (7th edition):

A sturdy tree with a picturesque head fifty to seventy feet tall… Originally to be used as silk moth food, but as this experiment failed, the tree proved to be so stately, graceful, and ornamental that it was soon valued for its own sake… The pistillate (female) trees in autumn are loaded with great clusters of seeds, being reddish samaras; it is both conspicuous and beautiful. It is a tree of great merits. It retains fresh, bright foliage into late summer where many other trees are ragged and unsightly… It delights in meager and barren soils (ash fills, rock rip-raps, industrial dump sites, reinforcement embankments), where few other trees can grow. It has no insect pests or diseases… The loveliness of its unfolding young leaves with their bronze green and madder browns with pale green tips glow in a brilliant atmosphere like the wings of a golden pheasant. Bring one into the house, put in to a proper vase, set in the sunlight, and you will have a bouquet rarely equaled.

I am going to relate several of my researched items, which I would like for you to read with an open mind, and hopefully decide to cease and desist the mindless, expensive, and misdirected war against a tree species.

First, even though Ailanthus has many glucosides and is allelopathic (can affect other plants with these chemicals), the actual most noticeable result is that it enriches forest soils so that other tree seedlings grow better. And any deleterious effect drops to zero only five feet from the base of the tree. Keep in mind that members of the family Simaroubaceae are known to produce compounds with a wide range of effects upon insects, viruses, fungi, protozoa, and cancer cells. Ailanthus produces at least ten quassinoids (a group of natural chemical compounds; some are used in cancer therapies)! I would never attempt to get rid of any plant with such untapped potential. The nutrient availability from dropped and dead leaves, branches, bark, etc. as decayed litter is four times higher than other native trees.

Second, it is well known that with a three-foot tap root on a three-inch seedling (I dug it up myself), Ailanthus can establish, survive, and grow faster on poor, reclaimed soils, industrial ash, and ballast placement retentions (like highways and railroads) than any other tree species in the world.

Third, Ailanthus produces biomass quicker than even quaking aspen or Paulownia. And when it is harvested, it recovers by producing even more “stump sprouts” than silver maple.

Fourth, Ailanthus establishes trees in forested areas only in the case of severe harvesting or very large blow downs. It needs full sun to survive. On my own home property, thirty-five years ago, I came to live with a pasture and a large Ailanthus tree (let’s say fifteen-years old), and even though I was well aware of its reputation, I decided to observe, rather than to listen to others. Now, I can add thirty-five years to that tree, and just today I counted the proliferation of successful sprout trees – there were eighteen. Of these eighteen, six will be successful and have a decent crown and a trunk diameter of eight to ten inches. Another six are tall and straight but with diameters of only four to six inches (straight and clear for at least one sixteen-foot log). The remainder show poor growth, scarred by buck rubs, losing the battle with grapes, diameters of only two inches at most, and are suppressed. I would hardly call this invasive when confronted with large acreages of pure stands of black birch, tulip poplar, white ash, and even wild black cherry.

Fifth, the tree has an odor which makes a rather good final identification feature. I’ll call to your attention that the best identification for all Prunus (especially black cherry) is the bad smell of a broken twig. Also sassafras, birches, spicebush have definitive odors. As to the odor of male flowers – I once had a client who was about to cut down his chestnut trees because he couldn’t stand the flower smell.

Sixth, Ailanthus breaks quickly, and if you are an arborist – beware! However, it is not one of the top three broken branch trees after a storm. They are Chinese elm, willow, and silver maple. Its wood is very suitable for plywood and it is the top candidate to survive urban and industrial pollution. Its wood properties have been considered similar to white ash.

Seventh, again I will quote:

It is an important timber and fuel wood tree… And it is planted for timber and reforestation in New Zealand, the Middle East, Eastern Europe, South American, and other places. Ailanthus is yellowish-white and well-suited for cabinet making. The mature wood of Ailanthus is of proven quality for furniture, musical instruments, and other wooden ware. This species is easily worked with tools and glue, and takes a finish well. When kiln dried properly, it offers the ability to be used in a wide variety of wooden structures.

For those of you involved in the great Ailanthus “search and destroy,” you might consider other ubiquitous trees to mark – ash-leafed maple, Amur cork tree, white mulberry, Chinese elm, Norway maple, and many others.