Potomac Palisades, DC

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#1)  Potomac Palisades, DC

Postby Darian Copiz » Mon Sep 07, 2015 6:03 pm

The bluffs along the Potomac River and the adjacent neighborhood in Washington, DC are known as the palisades. I measured trees occurring in wooded areas here (with a few open grown trees as well) between December 2014 and March 2015. Most of the woods occur on the steep slope between the top of the bluffs and Canal Road which runs along the bluffs’ base. An old trolley line, which had opened in 1895, used to run along the top of the slope for much of its length. It was decommissioned in the early 1960s. There has been some controversy about whether or not to make this a more formal trail. In the meantime it stays open, relatively unvegetated, and is a means of traversing the palisades. Closer to the Maryland line, the Georgetown Branch of the Baltimore & Ohio railroad climbed up along the slope. Now it is the Capital Crescent Trail. Various sections of the bluffs had been quarried in the past, leaving cliffs and rock outcroppings. Civil War fortifications had been installed on the heights above Chain Bridge. Despite the multiple causes of disturbance, some patches of older trees still occur on sections of steep slope and in some of the small stream valleys emptying into the Potomac.

The hollowed out trunk of this tulip tree was 18' 8" in diameter. Based on its position in the woods and old maps of the area, I believe it used to grow along an old fence row or property line.

As with the District portion of the Chesapeake & Ohio Canal, I measured trees that had a large cbh for the species, were uncommon, or appeared to be tall for the area. I measured a total of 147 trees consisting of 28 species. Making tree measurements in this area was often not very pleasant. The steep slopes made it necessary to walk down around some trees and back up the slope to get a tape around the trunks. There was a lot of dense undergrowth, including quite a bit of greenbrier. These conditions combined in some cases to make throwing the tape to the other side of the tree the only reasonable alternative for taking a cbh measurement. During one such toss around a tree, I gashed open my hand on greenbrier thorns, getting blood all over the tape. In another case I estimated the cbh (and noted such) as it was right at the edge of a cliff, and wasn’t worth risking maneuvers to try and measure it. Some trees were also in close proximity to traffic and people’s backyards – or at least what they might think are their backyards. While walking along the old trolley right of way, I became a bit uncomfortable the first time I saw a pack of dogs approaching. Then I saw their walker, which put me at better ease. Although the right of way is used, one comes across people infrequently.

This 1892 map from Evans & Bartle shows a wooded area along Maddox Branch. An earlier map surveyed by A. Boschke in the late 1850s also showed this as being wooded. From the current position of some of the older trees on the site, it appears they may have been growing along the property line to the west of the stream.

Overall, the tree heights and girths were slightly greater than that of the Potomac floodplain below. This is mostly attributable to sections of older trees, but also to greater overall diversity. On the other hand, the open southwest facing exposure in much of the area would tend to limit girths and heights. The section with the highest concentration of big trees was the stream valley of Maddox Branch, which is easily accessible and has a footpath running through it. Many of the large trees here were growing more or less in a line along the west side of the stream. I believe some of these may have originally been semi-open grown trees along a fence line or property line. Behind this line was a small section of woods which appears to have been relatively undisturbed for over 150 years. There are a few other small areas along the palisades which may have a similar age. Other interesting sections included a grove of willow oaks on the slopes east of Arizona Avenue (what used to be Davis’ Branch) and some larger trees near the Georgetown Reservoir.

The RI for height is 113.3'

The RI for girth is 13' 11"

The height Rucker Index is 113.8 feet. The girth Rucker Index is 13 feet 11 inches. As is often the case, the large old tulip trees were the most impressive. What stood out most about the site though, was the number of large black cherries growing on the disturbed slopes. Cherries in the DC area are often not a very large or long-lived species, and many of the cherries along the palisades were in decline. The period since disturbance may have been about the right balance to produce trees that were large, but not quite dead yet. I measured 5 black cherries with a dbh over 3 feet. An uncommon tree I measured was a hackberry, which based on its form appeared to be Celtis tenuifolia. However, I have not yet confirmed this and it could possibly be C. laevigata or less likely C. occidentalis. Near the Maryland border, there were also a few Quercus muehlenbergii, which are not common in the area.

I previously mentioned that the palisades was not the most pleasant place to make measurements. However, it was definitely interesting, with a lot of history – and signs of history, some discoveries of nice trees, and good views of the Potomac below.

This tulip tree was 14' 6" cbh. It would have been more if not hollow. The second tree to the left of this one, in the background, was 18' 8", also a tulip tree, and also hollow. A trail in the foreground runs around the tree.

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#2)  Re: Potomac Palisades, DC

Postby Matt Markworth » Thu Sep 10, 2015 6:51 pm


Thanks, I very much enjoyed reading your report. I guess Tuliptree reigns supreme in yet another location!

Great to see chinkapin oak being represented. There's a very old, open-grown specimen near me and it holds its own, in terms of character, in comparison to other nearby old, open-grown oaks such as bur, white, and swamp white.

I love how trees just continue on making their own history, oblivious to all the human history that is being made around them.


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#3)  Re: Potomac Palisades, DC

Postby Jess Riddle » Sun Jan 03, 2016 2:16 pm


Great post!  I was reviewing our records, and some of these trees are quite large compared to what we've previously measured.  What kind of environment did the basswood, black locust, and white oak grow in?  You mention some trees may have been planted or been left along fence lines, so I'm wondering if these trees grew entirely in a forest or if they were adjacent to open areas for an extended period.

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