Barking Up A Bridge

On September 11, 2010, the Bob Dunning Memorial Bridge was constructed in true barn-raising fashion. The bridge is a key feature of Pondicherry Park in downtown Bridgton.

bridge, summer

Bob Dunning, who died suddenly, was a builder, an artist, and among other things, a teacher–sharing his craft with students young and old.

bridge 1bridge 2

bridge 3bridge 4

bridge 7bridge 5

bridge 6

To honor Bob, who treasured traditional building techniques, his friends and fellow craftsmen designed and built a covered bridge leading into the park.

bridge beams

“As the poet said, ‘Only God can make a tree’–probably because it’s so hard to figure out how to get the bark on.” ~Woody Allen

One of the unique things about the bridge is that each tie beam comes from a different tree species, with the bark left on. As I walk across the bridge, my eyes are always drawn to the beams.

Until I took the Maine Master Naturalist class, I recognized only a few species by their bark. But my eyes were opened to the fact that each species has its own presentation, which is true for everything in the natural world. I wanted to know all of them so I set out to teach myself, beginning with the species on the bridge. These became the focus of my capstone project for the class. I spent hours upon hours pouring over reference books such as BARK by Michael Wojtech, The Tree Identification Book by George Symonds, Manual of Trees of North America by Charles Sargent and Forest Trees of Maine by The Maine Forest Service.

I sat in front of trees and sketched them, trying to gain a better grasp of their nuances. I dragged foresters into the field and picked their brains. And I drove hiking companions crazy as I tried to point out clues.

The result was a brochure that you can pick up at the kiosk (let me know if you can’t find a copy) and a powerpoint presentation that breaks down the species by types of bark. Did you know that there are seven types of bark? I learned that from Wojtech’s book and it made it easier to note the differences.

image

Follow me now, as I take you across the bridge and give you a glimpse of each tree. We’ll begin on the east side (closest to Renys) and work our way west.

Beam 1, cherry, smooth bark breaks into scales that are curled outward on the edges. outer scales begin to flake off, revealing smaller, darker, irregularly shaped scales without prominent lenticels

beam 1 e, black cherry

Beam #1: Black Cherry (Prunus serotina): Scales; gray-brown to almost black; small, rough scales randomly placed; curled outward like burnt cornflakes or potato chips.

Beam 2, yellow birch

beam 2 e, yellow birch

Beam #2: Yellow Birch (Betula alleghaniensis): Peeling/Curling; bronze to yellowish-gray; curls away horizontally into thin, papery strips; shaggy appearance.

Beam 3, red maple,smooth, light to dark gray, vertical cracks

red maple

Beam #3: Red Maple (Acer rubrum): Vertical Strips; light to dark gray; almost smooth or cracked vertical, plate-like strips; curls outward on either side; sometimes bull’s eye target caused by fungi.

BEam 4, American BAsswood, GRay to brown, Narrow furrows form long, flattened ridges with parallel edges, ridge surface broken horizontally by hairline cracks, often into squarish segments, ridges loosely intersect

Basswood bark

Beam #4: American Basswood (Tilia americana): Ridges; gray to brown; flattened, square-like ridges with parallel edges; may intersect like a woven basket every 6-12 inches.

Beam 5, red oak, rough, dark brown to blackish furrows, sepaprate smooth, light-colored, often lustrous ridges flush with circumference of trunk or slightly concave, ridges like ski tracks, loosely intersect

beam 5 e, red oak

Beam #5: Northern Red Oak (Quercus rubra): Ridges and Furrows; light colored, with rusty red inner bark; wide, flat-topped ridges run vertically parallel like ski tracks; dark, shallow furrows separate ridges.

Beam 6

hemlock

Beam #6: Eastern Hemlock (Tsuga canadensis): Scales; cinnamon-red to gray; rounded or irregularly-shaped scales; inner bark has purplish tint.

BEam 7, beech, light gray to bluish gray, smooth and unbroken

beam 7 e, beech

Beam #7: American Beech (Fagus grandifolia): Smooth/Unbroken; silver-gray or grayish-green; sometimes blotched with lichen; carved initials remain visible forever; often pockmarks caused by fungi.

Beam 8, Ash, gray to brownish-gray diamond-shaped furrows, resembles woven basket.

ash

Beam #8: White Ash (Fraximus americana): Ridges and Furrows; ashy-gray to brown; intersecting ridges form obvious diamond-shaped furrows; look for letter “A” or pattern of cantaloupe rind.

BEam 9, white pine, dash-like lenticels, turns gray to reddish-brown, thick, irregular shaped scales, turn out, develops fine, horizontal lines/cracks consistently spaced like writing paper.

eastern white pine

Beam #9: Eastern White Pine (Pinus strobes): Scales; dark gray to reddish-brown; thick, irregularly-shaped scales; fine horizontal lines evenly spaced along scales like lines on a legal pad.

BEam 10, Red Pine (Norway), reddish brown to pinkish, irregular, thin, flaky scales like jigsaw puzzle, surface of blocks roughly aligns with circumference of tree

red pine

Beam #10: Red Pine (Pinus resinosa): Scales; mottled red and grayish-brown; flaky scales; jigsaw puzzle or sandstone appearance.

BEam 11, sugar maple

sugar maple

Beam #11: Sugar Maple (Acer saccharum): Vertical Strips; gray to brown; finely cracked; looks like old paint; curls away from trunk on one side; look for horizontal scars indicating work of maple sugar borer.

BEam 12, poplar, Big-toothed aspen, deep furrows, rough and more rounded?

beam 12 e, big tooth aspen

Beam #12: Big-Tooth Aspen (Populus grandidentata): Ridges and Furrows; greenish-brown to dark gray; V-shaped furrows intersect every 6-12 inches; flattened ridges appear sanded down; gnarly look; periodic horizontal lines; on older trees resembles Northern Red Oak at bottom and Birch toward top.

BEam 13, white oak, light gray, can appear whitish with a reddish cast, furrows form flattened ridges, broken into somewhat rectangular-shaped blocks, furrows steep and narrow, with sides of blocks often parallel, old bark+irregular in shape, might look like shingles

beam 13 e, white oak

Beam #13: White Oak (Quercus albra): Ridges; light gray with reddish cast; rectangular-shaped blocks with flaky surfaces; ends of blocks curl outward; feather-like in mature trees.

Beam 14, elm

beam 14 e, American Elm

Beam #14: American Elm (Ulmus americana): Ridges and Furrows; ashy-gray; diamond-shaped furrows; flat-topped ridges; alternating light and dark layers like vanilla and chocolate wafer cookies.

BEam 14, black birch

beam 15 e, black birch

Beam #15: Black Birch (Betula lenta): Lenticels Visible (note: all trees have lenticels, but they are more obvious on some than others. Lenticels are tiny slits in the bark that allow for gas exchange, just like our pores); gray to brown-gray to black; may crack and form scales that curl away from trunk; long, thin horizontal lenticels.

Beam 15, paper birch, white birch

beam 16 e, paper birch

Beam #16: Paper Birch (Betula papyrifera): Peeling/Curling; white to creamy white; peeled bark reveals pink or orange tints; small, horizontal lenticels visible.

That’s it in a nutshell. Ah, but here’s the thing. Except for the American Beech, tree bark changes as a tree ages. And beech trees can be equally confusing because some are severely affected by beech scale disease. So, just when you think you know a species, you may come upon a younger or older version and get totally thrown off. The key is to take your time, walk all the way around the tree, and look at other clues like the twig and bud formation. Touch the bark. Smell it.

And take a walk across the bridge and into the park during any season. Chances are, I’ll be there doing the same.

bridge to park

Thanks for joining me for this lengthy wander. I hope you’ll find time to wonder about bark.