Cornell Urban Horticulture Institute Team Evaluates Condition of National Mall Elms

Cornell UHI team Barbara Neal, Bryan Denig, and Nina Bassuk assess the health of one of the iconic elms ringing the National Mall. Photo by Yoshiki Harada

In April 2018, the Cornell Urban Horticulture Institute team of Nina Bassuk, Bryan Denig, Yoshiki Harada, and Barbara Neal released an extensive report on the elms (including American elms) of the National Mall in Washington, D.C. The report details a study conducted at the request of the National Park Service to examine the current conditions of the trees and soils on the tree panels of the National Mall, and it includes a fascinating history of the landscape. Here are some highlights from the report.

The National Mall elm trees are an important planting in the monumental core, yet they face several challenges. The soils of the tree panels are very compacted, most likely due to the constant pedestrian use and the numerous large organized events that take place on the Mall. Unevenness in the size and distribution of the tree canopy has resulted from decades of mortality (often due to Dutch Elm Disease) and the planting of certain elm varieties with growth forms that are seen as incompatible with the planting as a whole.

From June 17–20, 2017, the research team conducted a tree inventory and collected soil data and samples for later analysis. In addition, in November 2017, ground penetrating radar done by Council member Gary Raffel was used to document root growth for seventeen of the trees. This report deals with the current tree and soil conditions, while management recommendations are in a separate report to be released in late 2018 or early 2019. 

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Essential and Updated: The Cornell Woody Plants Database

Like me, you may have a dog-eared, well-worn copy of the Urban Horticulture Institute’s (UHI) Recommended Urban Trees: Site Assessment and Tree Selection for Stress Tolerance. Another fantastic resource for urban foresters and UF volunteers that has just been updated is the Cornell Woody Plants Database.

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Nina Bassuk says, “What makes the site unique is its focus on matching woody plants to site conditions, a feature sometimes lacking on other plant selection sites and a consideration that is sometimes lost in the design and plant selection process.” With its extensive image collection and cultural information, the site is also very useful for woody plant ID and study.

Each entry includes ultimate size and shape, USDA Hardiness Zone, light requirement, salt tolerance, moisture tolerance range, insect and disease considerations, and key ornamental features. Impressively, each entry has Nina voicing a short audio lesson that reinforces ornamental and ID features. Nina says this is a work in progress, as she is re-recording some of the entries for better audio quality.

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There is a Course Plant Walk section, which you can use to find a series of plant walks through the beautiful Cornell campus based on different criteria like species (e.g., oaks, maples, and rosaceous and flowering trees) or tolerances (e.g., dry site and wet site trees); click on Maps to see the walk route.

The database was originally the outgrowth of the year-long joint Horticulture/Landscape Architecture (LA) course, “Creating the Urban Eden,” taught by UHI Director Nina Bassuk and Dept of LA Chair Peter Trowbridge.

The site had modest beginnings as an “online textbook” circa 2000. The first version consisted of a FileMaker Pro database running on the Cornell network from a Mac under a desk in the main offices of the Department of Landscape Architecture. Since then, the site has grown significantly more sophisticated with three major revisions that added additional features and functionality. The most recent upgrade was supported by a SUNY Innovative Instruction Technology Grant in 2013.

Check out the Cornell Woody Plants Database!

A young 'Canada Red' Prunus virginiana
A young ‘Canada Red’ Prunus virginiana

Cornell Urban Hort Institute: Interesting Research Continues Apace

The Council’s longtime Board member and beloved speaker, Nina Bassuk, gives us an update on three areas of research underway at UHI. Dr. Bassuk will be the plenary speaker for the NYSUFC Conference this July. (Register now for best rate!) 

UHI researchers are attempting to fast-track propagation of alkaline-tolerant oaks that should come onto the market in the next five to ten years.
UHI researchers are attempting to fast-track propagation of alkaline-tolerant oaks that should come onto the market in the next five to ten years. Photos Courtesy UHI.

New Oaks for Tough Sites 
Dr. Nina Bassuk founded and directs Cornell’s Urban Horticulture Institute (UHI) and conducts applied research in the areas of plant improvement, transplanting technologies, and soil remediation.  “We think of everything we do in terms of potential practical value to the field,” she says.

For example, owing to hybridizing work UHI has been doing since the early 1990s, some oak introductions will be coming onto the market in the next five to ten years that could be game-changers: a whole series of oaks—not just English and bur oak—that can tolerate a pH of 8.0! That means oaks with foliage that stays green in the alkaline soil conditions prevalent in urban settings (and we are increasingly recognizing that in terms of plant stress, “urban” conditions are everywhere—not just in cities.)

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