Elm tree lovers find new hope Research: Scientists have developed two varieties of elm tree that are more resistant to Dutch elm disease. Nurseries probably will have the "Valley Forge" and "New Harmony" varieties in a few more years.

Sun Journal

June 30, 1996|By Dennis O'Brien | Dennis O'Brien,SUN STAFF

Sixty years ago, a beetle-borne fungus arrived in the Unite States and began killing off Ulmus americana, the American elm.

Dutch elm disease slowly destroyed the shady ambience of town squares, parks and college campuses. The infection wilted leaves, rotted limbs and eventually wiped out nearly 80 million trees.

Now, scientists may have developed a solution. Researchers at the National Arboretum in Washington have created two varieties of elm tree that seem more resistant than any others to Ophiostoma ulmi, and thus may allow a comeback for the elm and the notably beautiful landscape it provides.

"It's not a cure -- it's a tolerant strain," says a cautious Alden M. Townsend, the U.S. Department of Agriculture geneticist who created and named the two new species -- the "Valley Forge" elm and the "New Harmony."

Townsend began breeding elms at the Agricultural Research Service's research center in Delaware, Ohio, 20 years ago. It is a process that does not lend itself to great speed. He crossed the seeds of thousands of trees from across the country that showed resistance. The trees grew for three to six years at the 200-acre site. When they reached a height of about 10 feet, he injected them with Ophiostoma ulmi.

He then checked to see which varieties avoided the symptoms: browning, yellowing leaves, leaves that fall prematurely, branches that wither.

"Valley Forge" and "New Harmony" probably will not be available from nurseries until 1999, after the seedings are grown by nursery wholesalers. But the two strains are heartening news for those who believe that the elm has no peer when it comes to providing oxygen and atmosphere.

The oak -- called the "mighty oak" so often that the phrase has become a cliche -- is stouter and has limbs that are more gnarled and can give it a ghostly, menacing appearance.

The maple is more colorful, particularly when fall's chilly temperatures transform its leaves into bright reds and yellows. But with 125 species, the maple has multiple personalities. The Audubon Society's "Field Guide to North American Trees" acclaims the red maple as being "most spectacular in autumn." But the silver maple is panned for being brittle and having a form that is "not generally pleasing."

The same guide describes the American elm as "large, handsome, graceful."

American elms are usually recognizable for their long trunks, and a vase-like shape -- formed by branches ascending from the trunk like streams of water shooting up from a hose. The trunks can be 4 feet in diameter and the crown 120 feet in height.

But statistics cannot describe the elm's effect on people.

"There's something about the elm. It's a beautiful tree and it's done its job -- giving shade in an urban environment -- remarkably well," says William F. Monroe, a 72-year-old Cincinnati businessman who remembers elms shading the streets in the New England towns where he grew up. When he returned last month for his 50th reunion at Williams College in Williamstown, Mass., he toured the campus to check on the health of the trees.

Dutch elm disease arrived in the United States in the 1930s by way of a shipment of diseased elm logs from France.

The elm bark beetle was often the agent that spread it.

"It's really had a tremendous environmental impact," says Townsend. As evidence, he offers two color slides that show the "before" and "after" of Dutch elm disease in a suburb of Detroit. One slide shows a leafy, tree-shaded street. The other, taken three years later, shows a stark, brightly lit street at high noon, where somehow even the parked cars look deprived of shade.

Yet it is not the past, but the future, that has many elm lovers concerned.

Disease kills 25 to 30 elms a year on the Washington Mall and around the capital's national monuments -- despite daily checks by National Park Service crews for early warning signs of disease. Baltimore is losing about 200 elms a year.

With 2,500 elms on the mall and near the monuments, the elm ranks second in number to the cherry tree (which number 3,000). But it probably adds more atmosphere than any other species.

"The elm is what gives the monumental core its character," says James Sherald, a plant pathologist with the National Park Service in Washington. "It's the lattice work of sorts for the whole system."

"The way I see it, we'll have no more American elms unless these new varieties do the trick," says Marion Bedingfield, a tree service technician with Baltimore's Department of Recreation and Parks.

Townsend's new varieties are not the first elm species to be commercially developed: A "Liberty elm" was developed by researchers at the University of Wisconsin in 1983 and is marketed by the nonprofit Elm Research Institute in Harrisville, N.H. A "Princeton elm" was developed by a Princeton, N.J., nursery in 1922.

Baltimore Sun Articles
Please note the green-lined linked article text has been applied commercially without any involvement from our newsroom editors, reporters or any other editorial staff.