During their usual strolls along the main streets of their home towns, our parents and grandparents gazed at the scenery around them and took for granted a spectacular picture that is seldom observed nowadays and that few of us can hope to see during our lifetimes. The interweaving limbs of the stately trees that lined the streets ascended into a towering canopy with a graceful, arching beauty unmatched by any tree that is commonly seen today, spreading horizontally at heights often greatly exceeding 100 feet (in rare cases attaining 140 feet with even greater spreads and 11 foot trunk diameters), and drooping long, slender branches in abundance high above the street, blocking all view of the sky. Along countless streets for many miles in cities and towns throughout the tree's extensive native range in the eastern half of North America, even as late as the early 1960's, this scene abounded, the effect of the only species capable of giving us such majestic splendor.
Veritably the standard against which the merits of other shade trees were measured, the American elm provided the ultimate in stateliness and beauty, making it the single most popular shade tree for lawns and city streets in the eastern United States, and earning it distinction as the state tree of Massachusetts and North Dakota. Architects even designed buildings with elm plantings inherent in their plans. The early citizens of Portland, Maine and New Haven, Connecticut had such a passion for the American elm that they created elm-lined streets on practically every block and earned each city the nickname, ?City of Elms.? Once as naturally abundant as maple, oak, and pine, the American elm was an essential part of our natural landscape and cultural heritage throughout the first few centuries of our history, and it was in fact the first symbol of our national independence; for a fine example had stood in Boston as the famous ?Liberty Tree,? an emblem of promise and a gathering site for patriotic citizens intent on independence, until British soldiers destroyed it as a final act of hostility during a hurried retreat from Boston in 1775.
Many of us remember how painful it was for our communities to witness the tragedy that recurred throughout the eastern states during the 1960's and
1970's. Many remember watching helplessly as countless main streets, parks, historic sites, and neighborhoods that had been so handsomely graced with fine elms were transformed within a few years into barren, urban-looking landscapes devoid of trees, the result of a frighteningly efficient epidemic that had appeared suddenly. We can imagine the profound dismay of the citizens of Portland and New Haven as each ?City of Elms? was quickly transformed into a ?City of Firewood,? necessitating almost phenomenal removal expenses. Some may recall marveling at the futility of the ?cut and burn campaigns? which were initiated to halt the spread of an epidemic which was killing trees literally by the millions each year.The cause of this pervasive syndrome of wilt and dieback was a parasitic fungus. The spores of the fungus were being deposited into the vascular systems of healthy elm trees through twig-crotch feeding wounds chewed by elm bark beetles, the carriers of the disease. Once in contact with the inner bark, the spores germinated into rapidly growing fungal threads which invaded the entire conducting systems, clogging them and preventing the transport of water and nutrients to the hosts' crowns, thereby killing the trees in a manner not unlike that of the chestnut blight. Unlike the chestnut blight, however, the elm pathogen proved efficient at destroying the root systems of its hosts, preventing them from sending up new shoots, and it even was observed to spread to adjacent trees through natural grafts between their roots.
A native of Asia, the fungus first had appeared in North America in 1930 in Cleveland, Ohio, having found its way into the continent by the same means as the chestnut blight, through the accidental import of infested logs from a related species. The parasite was no stranger in Europe, where it similarly had appeared early in the century, and where its pervasive devastation of a number of European elm species, including the esteemed Dutch elm hybrids which had lined many streets, had given rise to its now-familiar name, ?Dutch elm disease.?
The various elm species native to Asia, where the so-called ?Dutch? elm disease originated, are highly resistant to this disease, as healthy specimens are able to manufacture chemicals which prevent the spores from germinating or gaining a stronghold in the inner bark of the trees, and they consequently are able to thrive with little or no stress in the face of generations of exposure to the disease. In its native Asia, the disease actually serves the valuable function of eliminating old or weakened elms to make way for new growth. The Dutch elm disease fungus, like purple loosestrife and water hyacinth, thus provides us with yet another classic illustration of the danger inherent in the introduction of an organism into an ecosystem that is not its own.
Nowadays we have to search rather painstakingly to find an occasional large surviving American elm tree, as the pathogen's destruction of more than 100 million American elms during the last few decades has effectively depleted the population throughout the tree's natural range. Inevitably, the continuing pattern of destruction soon will threaten the survival of the species, for although young saplings are still common, the current population consists primarily of immature specimens with little chance of reaching a stately maturity, and the large, mature examples that still are seen occasionally are being eliminated rapidly. Like the American chestnut, which is now gone from the forest canopy, the American elm has been declining slowly but surely ever since the introduction of a lethal fungal blight, and although the threat of extinction is not immediate, we cannot realistically avoid the conclusion that the last of the sizable, wild American elms likewise will disappear within our lifetimes.
The development of purely American elm varieties with adequate resistance to Dutch elm disease remains the only hope for ultimately saving the species, as systematic injection with elm fungicide is an expensive, cumbersome, and unnatural process. It was fortunate, indeed, that such development proved possible and eventually yielded the American elm strains which now constitute the essential ingredients of my project. In other words, we now have a realistic means to ensure the ultimate survival of the American elm and to bring about the imminent return to our landscapes of fine, stately specimens that are likely to survive through the decades. That is the essence of my endeavor, and it is my hope that this writing will help to sow the seeds of this inspiration for others as well. Having obtained the wholehearted approval of my home town's conservation director, I have been raising these new elm varieties in quantity and have planted many of them in suitable locations in Acton, Massachusetts. My idea of a suitable location is an open area in which a tree always will remain safe from indifferent landowners and available for public appreciation in a rustic setting, and that means conservation lands, most notably the Acton Arboretum.
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