Part 2: 1950s - 1980s

Dutch elm disease and an uncertain future for Harvard trees

Harvard Yard today is by no means a uniform monoculture of elm trees. Records show that in 1973, the Old Yard (the area bound by Grays, Univeristy Hall, and Holworthy inside the major paths) had 34 elm trees (Ulmus spp.). 23 years later in that same area there are 20. The culprit behind the attrition of the elm trees is Dutch elm disease (DED).

Harvard (along with Main Street USA) decided to almost exclusively plant elm trees in the Yard. Several generations of elms have passed through the Yard in its long history. However, this generation may be the last. DED took advantage of the short-sighted planting of elm monocultures in this country. The vectors for this disease are the American and European elm-bark beetles. The beetle itself is relatively benign, but it's the fungus that it hosts and spreads that causes the problems. This fungus chokes off the vascular system of the trees, eventually killing it.

The culprit: the elm bark beetle (Harvard Magazine)

Harvard's first encounter with DED occurred in 1952. It took many years for the disease to slowly creep up the east coast. Harvard made one of the greatest understatements in its history that year when it said that it hoped that only a small number of the 700 elms on campus would be lost. The first casualties occurred that year in 1952 and have not stopped even today.

An elm comes down in front of Grays Hall circa 1952 (Harvard Alumni Bulletin, Harvard Archives)

A bold program was initiated in 1979 with the hopes of slowing down the loss of elm trees to DED. At that time there were only 285 elms were left on the campus. Harvard decided to spend more than $25,000 per year in an effort to rescue as many elms as possible from an early death. What does $25,000 include? Over half the amount goes towards spraying the branches and the leaves. The rest buys fungicide injections, fertilizations, and pruning. After 15 years of the program, only 165 elms remained, which makes a mortality rate for the period of 42% . The number is no doubt even lower today. While treatments can slow the spread of the disease in the tree, they cannot completely prevent it.

The predicted post-DED Yard in front of Holworthy in a computer generated image, 1989 (Kristina Hill and David Ruben, Harvard Magazine)

It is estimated that within 25 years, nearly all the elms will be gone. Many of these elms date back over 90 years. However, there is reason to still have some hope for the future of the elms. The main reason that DED was so quick and deadly in the United States was because of the monocultures of elm along streets and in parks. Even Harvard Yard was a near monoculture of elms. This provided large amounts of food and habitat for the beetle vectors and short distances between neighboring elms. DED did its work and today the elm no longer has the same role it one did in our forest and in our cities. Large mature trees like those in the Yard are uncommon today. There are fewer large elms and there is less density. One could predict that this might slow the spread of the disease to the point where an equilibrium number of elms might remain. Also, new, disease resistant cultivars of the American elm have been discovered and some are growing today in the Arnold Arboretum. Will there be a planting of the American elm on Harvard campus anytime in the future? It is certainly a possibility. Generations of Harvard students and faculty have fallen in love with the majestic elm, and its disappearance would be a sad chapter in Harvard history. With the fate of the elms sealed, only a progressive plan could preserve and strengthen the canopy for the future.

Go to Part 3: 1990s - Present - Taking action: planting the canopy for the next century

Sources:

General Information about Trees on Harvard Property. HUB 3848, Harvard University Archives.

Shaw, Jonathan. “Every Tree Doomed.” Harvard Magazine . July/Aug 1994. 46-53

Tredici, Peter del . “The Ecology and Economics of Elm Replacements in Harvard Yard.” Arnoldia. Spring 1998: 27-32.

 

Created by Ryan Lynch

Last updated February 28, 2007