Downtown, other urban trees require careful selection, care

Life on the street…it can be a rough existence. Even for trees.

Leafy city dwellers face a variety of assaults--from daily foot traffic pounding their roots, to the extreme weather events such as limb-busting ice storms and debilitating drought. Add to the list of stressors invasive insects--like the Asian longhorned beetle--or devastating disease, and it's a wonder there's any green life sprouting up from our cities at all.

That's why Agricultural Research Service scientists at the U.S. National Arboretum (USNA) have spent 4 years studying various trees for urban-worthiness. Along with several partners--including the U.S. Forest Service, the Maryland Department of Natural Resources, the University of Maryland, Washington, D.C.'s Urban Forestry Administration, and local utility companies--these researchers have found some varieties that should be as naturally at- home on the streets as a cabdriver in New York City.

Giving more weight to this work is the fact that trees, woody shrubs, flowers, and other ornamentals constitute one of the fastest-growing segments of U.S. agriculture. Sales of these plants soared to more than $16 billion in 2005, according to USDA's Economic Research Service.

What's called the "Power Trees Project" has multiple goals. Researchers involved are focused on finding appropriate plantings that are not only sustainable and low-maintenance, but also offer the many benefits humans want from green plants.

Even before their tree hunt began, USNA scientists knew what they wanted: cultivars small-to-medium in size, with solid pest resistance and a tolerance for environmental extremes. A seemingly tough task, but a modest one for researchers with decades' worth of tested varieties at their disposal.

"We considered many cultivars developed by arboretum scientists, such as maples, dogwoods, crape myrtles, elms, and cherry trees," says John Hammond, research leader of the USNA's Floral and Nursery Plants Research Unit in Beltsville, Maryland.

In addition to identifying species that are suitable for urban environments, the researchers wanted to find out which nursery cultivation method--container or traditional in- ground planting--best prepared saplings for a life on the streets.

"We found that nursery trees started in containers grew better at our test nursery than those started in open ground," says Hammond. "Container-grown trees, which can be set above or below the soil surface, don't generally suffer the kind of root damage as do trees that must be dug up and bound in burlap for transplanting."

Comparative survival and growth in street plantings at nine test locations will be evaluated over the next several years to see whether the growth advantage of the container- raised trees persists.

And despite their rugged nature, these trees are sure to wow city residents with either their soft spring charms or commanding autumn brilliance. Visit the Power Trees project at www.powertrees.com for more information.

This article was adapted from the Agricultural Research magazine published by the United States Department of Agriculture.

Editor's Note: Delta George is a K-State Research and Extension agriculture and 4-H extension agent assigned to Bourbon County. She may be reached at (620) 223-3720.