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Vol. LX, No. 24
November 28, 2008

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Want to know about some aspect of working at NIH? You can ask questions anonymously at (click on the Feedback icon) and we’ll try to provide answers.

Feedback: I am just curious: Could you explain NIH’s tulip poplar tree replacement procedure? It seems that the procedure is to prune them periodically until they become unsightly, and at that point the remaining crown is cut off and the rest of the tree (relatively tall trunk and roots) is allowed to die. Such a “topless forest” is located immediately north of the Bldg. 21 parking lot; another one south of that lot, as well as one north of the Vaccine Center, have trees in various stages of aging.

Response from Lynn Mueller, Office of Research Facilities landscape architect: First of all, ORF does all it can to keep all our campus trees alive and healthy. However, trees are living organisms and even under the best of growing conditions, all have a maximum life-span. ORF will prune and feed trees seen to be in distress. ORF does preventive and protective procedures too. Trees located along a construction edge are deep-root fed and crown-cleaned to help resist the possible environmental changes that may occur during and after construction. The Wilson Dr. tulip poplar trees were cared for prior to the Bldg. 33 utility tunnel project. Apparently the deep-tunnel excavation changed the groundwater flow causing the down-grade grove of poplars to eventually die back. No other cause could be determined. The Bldg. 40 poplars were also likely impacted by a nearby tunnel project.

Trees that die can be either cut down or turned into “snags” and used as wildlife attractants. Snags are the standing trunks of dead trees. Creating snags, where appropriate, also saves ORF at least half of the removal cost. Removal costs of a large mature tulip poplar can be $3,000 or more. Dead trees that are not near a “target” (parking lot or building, for example) can be used to attract wildlife such as woodpeckers and other cavity-nesting birds like titmice, nuthatches, wrens and bluebirds. These insect-eating birds will then help ensure that other nearby trees are cleaned of insect pests, thereby eliminating the need to spray pesticides. ORF has not had to spray any tree with an insecticide since 1989, possibly due in large part to this effort under the ORF Integrated Pest Management Program. The one exception was the application of Bt on selected oak trees in 1992 to control an outbreak of the invasive gypsy moth.

Under the NIH Master Plan’s tree preservation policy, ORF must replace any tree lost due to natural or man-made causes on a minimum one-to-one basis. Snags are considered lost trees and are replaced with native nursery-grown trees.

Starting in 1991, ORF began keeping records of trees lost and replaced. The count as of the end of 2007 was an overall campus gain of nearly 3,500 trees, with the current campus count at approximately 7,500 trees. Of those 7,500 trees, we have 152 different species not counting the numerous cultivars that some species have. Of those 152 species, 94 are native trees, or approximately 62 percent. All trees greater than one inch in caliper are tagged and identified on a GIS campus map. The maintenance history of each tree is kept.

ORF has been proactive in the management of our trees and has been recognized over the past years by several state, local and national arborist organizations for our innovations and management practices.

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