While doing some research on the land-use history of one section of the park I came across some interesting information and photos.  Our park keeps physical documents of the land acquisition transactions that took place when tracts were being bought and added to the canal boundary.  Among these records were appraisals.  These appraisals included timber values and documentation of all structures on a tract of land.  The timber appraisals even listed the number of trees over 14” dbh and the species, although it wasn’t always specific for some groups like maples and ash.  You could get a rough idea of the character of the forest at that time.  Pictures of structures were also included.  They were meant to document the structure only but some photos showed the surrounding landscape.  These photos and maps helped show the extent of disturbance during that time period.

One of the seasonal/recreational structures found along the Potomac River. This photo is from the 1970s. When the National Park Service obtained these properties most of these structures were removed.

I assisted a contract botanist with his survey on canal lands this month.  I always find it interesting to talk with botanists in the private sector about their experiences.  We had a successful couple of days surveying and found 6 new rare plant records for that portion of the canal.

View from atop one of the bluffs that was surveyed.

One of the plants we found was a new species for the park.  Aristolochia macrophylla is listed as imperiled (S2) for the state of Maryland.  The synonym for it is Isotrema macrophyllum.  Previous records for this plant in Maryland are from Garrett and Allegany counties.  This plant was found in Washington County which borders Allegany County.  After reading up on this plant I found out that is or was planted widely as an ornamental.  This information and the fact that the vines I found were near a lock and next to a pile of gravel, lead me to believe that this occurrence is probably an escaped population.   I ran into a similar situation with Kentucky Coffeetree (Gymnocladus dioicus) which is a state-listed tree but widely planted in the area.  I will include all this information in my records and still map the occurrence for the park’s database.  I also plan to reach out to the state botanist to get his opinion.

Aristolochia macrophylla (Pipvine)

Aristolochia macrophylla (Pipevine) climbing up a Sycamore tree.

Here’s an excerpt from a old plant guide I purchased this season that the interesting pollination strategy of this vine.

I didn’t get to catch this one in flower but I wish I did after reading this.

Lastly, I found this cool looking Sphinx Moth (Eumorpha pandorus) on a Hackberry (Celtis occidnetalis) leaf along the canal towpath.  I also found an early-instar Giant Swallowtail (Papilio cresphontes) caterpillar on the leaf of the state-listed (MD) shrub, Hop tree (Ptelea trifoliata).   The Giant Swallowtail is a state-listed butterfly in Maryland and I was glad to finally sight one.  The caterpillar’s strategy of disguising itself as bird poop is really interesting in my opinion.

Sphinx Moth (Eumorpha pandorus)

Giant Swallowtail (Papilio cresphontes) caterpillar

Those are the highlights from July.