Friday, July 20, 2007

Clinometers and tree height

A look at some of our stately giants

Posted Sunday, July 15, 2007

The second largest Osage orange tree in the country is at Hagley Museum. Danielle Quigley

Americans have a fascination with the biggest, equating it with the best. The United States is home to the world's biggest ball of twine, T-rex skeleton and disco ball. And we catalog our natural wonders by size, too. Since the 1940s, the nonprofit group American Forests has been documenting the largest known specimens of 826 species of trees. A listing of these champions can be found at the National Register of Big Trees ( resources/bigtrees). There's a 128-foot balsam poplar in Minnesota, a 141-foot red maple in Great Smoky National Park, but, alas, not a single Delaware tree in the registry.

But that doesn't mean our trees are puny. "From pre-colonial days, Delaware was primarily deciduous broad-leaf forest," says Dr. Sue Barton, University of Delaware Cooperative Extension specialist in ornamental horticulture. "Much of this wooded land has been lost to development, but tracts of old forest survive.

"So, although we may not have the nation's champion tree in any particular species, we certainly have a greater number of big trees than you'll find in Midwestern states that were originally prairie land."

The state has been keeping track of its own champion trees for decades. "Big Trees of Delaware," available online at forestry/forms/bigtrees.pdf, is a guide to the First State's champions, produced by a team from the Delaware Forest Service, including urban forestry coordinator Henry Poole, who contributed to the third, and most recent, edition.

"The guide is a way to draw attention to the state's biggest trees and get citizens interested in tree preservation," says Poole. "It was fun to put together, and people tell us it's a lot of fun to use."

Pore through its 69 pages and you'll discover that the state's tallest tree is a 166-foot yellow poplar at Winterthur Museum. But this poplar isn't the biggest tree in the state, as height is only one factor in what constitutes a big tree. Foresters also consider the trunk circumference and the average crown spread, using a formula to come up with the total points earned by a tree.

And, in case you were wondering, foresters don't need fire truck ladders or bucket trucks to measure the tippy-top of trees. They use clinometers, devices that measure the line of sight above or below horizontal.

The biggest white pine in the state is a specimen off of Way Road in Hockessin that has a 42-foot crown spread and a height of 124 feet. In contrast, the champion redbud tree, located at Hagley Museum, has a crown spread of 41 feet and is just 47 feet tall.

"It's all relative," says Barton. "As a species, redbuds are a lot smaller than white pine. Redbuds usually top out at about 30 feet tall, so 47 feet is pretty impressive."

One of Poole's favorite champion trees is remarkable for its circumference, not its height. A Japanese zelkova tree, located on a private estate in Greenville, has a circumference of 318 inches. "It's like no other zelkova I've ever seen," raves Poole.

Another one of Poole's favorites is an Osage orange tree at Hagley Museum that is the second biggest Osage orange in the country. This stout-branched tree has a circumference of 307 inches, a crown spread of 83.5 feet and stands 66 feet tall.

They may not qualify as champions, but Sue Barton's favorite big trees are the "string of pearls" along Kennett Pike that start in Greenville and extend to the state line. These stately old elms, sycamores and oaks were planted in the 1920s by Pierre S. du Pont, who funded the construction of Kennett Pike. The trees were a birthday gift to his wife, Alice, who remarked that the string of pearls she'd like best would be a string of handsome trees.

To see some of the biggest trees in New Castle County and nearby areas, plan to attend "On the Trail of Champion Trees," a day-long guided excursion on July 26. To register, call Longwood Gardens at (610) 388-1000.

Native Delaware is a weekly column by the university's Cooperative Extension on First State plants, animals and weather. McDonough is a communications specialist for the University of Delaware. To suggest a topic or ask a question, please contact McDonough at 831-1358 or
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