The morning of May 2 I set out for a quick survey of the greater Carderock area, with the goal of shooting some long-tube valerian, a highly state rare/endangered species that grows in several different locations in the Potomac gorge.

Along the way, on the towpath between the Billy Goat C and Billy Goat B trailheads, I noticed that a lot of trees along the stone retaining wall were missing.

What the heck? Wondering why, I decided to call the park and inquire when I got home.

I didn’t need to. A few hours later, on the way back, I saw a ranger taking photos, so I asked him about it. In summary, the retaining wall is historic, and it’s been in danger of being damaged by the trees, some of them were quite large. If one had gone down in a storm, the root mass lifting out of the ground could have caused a breach in the wall. Not only would that severely damage the canal and make that part of the towpath unusable, but an 8′ diameter sewer main, part of the Potomac Interceptor sanitary system, runs along there. It, too, would be severely damaged by a breach in the wall.

The flags marked a line 20 feet from the base of the wall; all the activity is being kept within that zone. They will be installing some monitoring equipment in order to track changes to the wall in coming years.

My main concern, of course, was damage to plant communities. Good news: the park always has an expert come in for a plant survey before they do any work.

Annoyingly the narrow strip of land between the towpath and the wall gets moved every few weeks, but if you go now, you’ll see some lyre-leaf sage blooming in there. The plants are quite short, but year after year they survive the mowers.

The spring ephemerals are almost entirely gone, just a few spring beauties left. Observed blooming on May 2:

• wild blue phlox (waning)
• star chickweed
• Virginia waterleaf (just starting)
• Coville’s phacelia (past its peak)
• long-tube valerian
• clustered snakeroot (just starting)
• golden Alexanders (S3 – rare to uncommon)
• rattlesnake weed
• hairy beardtongue
• moss phlox (waning)
• field chickweed
• wild geranium
• rue anemone
• lyre-leaved sage
• Rubus species (probably a dewberry)
• azure bluets
• dwarf cinquefoil
• plantian-leaved pussytoes (waning)
• bastard toadflax
• fringetree
• deerberry
• alumroot
• violet wood sorrel
• wild pink (a day or two away from being done)
• spring forget-me-not
• Virginia spiderwort
• common wood sorrel
• Philadelphia fleabane