Monday, April 21, 2014

Northfield's Boulevard Trees

“Northfield is a city rich in trees,” Harvey Stork wrote. “Looking eastward from Manitou Heights, one sees in summer a green grove broken only occasionally by the steeple of a church, the tower of a school, or the roof of a commerical or factory building. It seems hardly possible that this forest shelters a population of five thousand people.”

In July 1948, Stork counted “2,426 trees of 48 different species growing in the parking between the sidewalk and curb;” in other words, boulevard trees. Of these, the most numerous species in 1948 was the American elm: Stork counted 993 of them. Sixty-one years later, few of those elms remain. Most fell victim to Dutch elm disease, which was just beginning to make an appearance in Minnesota when Stork made his inventory.

Since Professor Stork wrote The Trees of Northfield in 1948, the population of the city has grown fourfold, but Northfield is still sheltered by an urban forest. In February 2014, forester Katie Himanga completed an Urban Forest Asset Management Plan for the City of Northfield (available here as part of the February Environmental Quality Commission packet), in which she inventoried 15,308 boulevard trees in Northfield. Of these, the most common species are maple (4292) and ash (3196).
from K. Himanga, CF, "Urban Forest Asset Management Plan."
City of Northfield, Minnesota. February 3, 2014.
Maple and ash are both attractive, relatively fast-growing species native to this part of Minnesota. Unfortunately, all varieties of ash are, in Himanga’s words, “susceptible to emerald ash borer (EAB) and are likely to become infested in the coming decade.” As was the case with Dutch elm disease, the emerald ash borer infestation will undoubtedly change the shape of Northfield’s urban forest.

Sibley Drive from the west.
On the east side of Northfield, Sibley Drive is a pleasant, well-shaded residential street that connects with Maple Street directly opposite Sibley Elementary School. There is no sidewalk on either side of Sibley Drive, and nearly all the boulevard trees are either maple or ash.  In the photograph above, you can see how the trees (mostly ash on the right-hand side of the street) appear to be planted exactly along the path of a possible sidewalk. It’s as if the street were designed to discourage foot traffic, including children walking to the nearby elementary school.  On the other hand, there is a good trail through Sibley Swale Park that runs roughly parallel to Sibley Drive, providing connectivity for pedestrians and bikers.

The high density of ash trees on Sibley Drive remains a significant problem, as it does on many of Northfield’s streets. In her report to the city, Himanga recommends a program of removing ash trees on boulevards and city parks (at an estimated cost of $1.8 million) and replanting of disease-resistant species (at an estimated cost of $340,000).

Related post from five years ago (April 25, 2009): The Trees of Northfield

The sound of spring peepers in Sibley Swale:

8.39 miles on Tuesday, April 15, 2014
The route:

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