21 October 2025

It was a hard summer for Panther Hollow Lake in Schenley Park. In early July I wrote What’s Wrong With Panther Hollow Lake? about the many challenges it faces due to sediment, low water and the concrete edge. Its problems were exacerbated by summer’s drought and heat making it impossible to ignore the pond’s ugly surface of filamentous algae (pond scum) and duckweed. This month I noticed another challenge lurking below.

Last Friday duckweed (Lemnoideae) covered most of the water.

But we have two helpers eating it now. A pair of mallards.

This is what they’re eating.

At the railroad (west) end of the pond I could see into its shallow depths and finally realized that Panther Hollow Lake is choked with invasive hydrilla (waterthyme).

The water looks stagnant but the plants do move.

Hydrilla is a problem in many Pennsylvania waterways.

Hydrilla moves from lake to lake on boats and gear. Fishing gear is a likely source of it since hydrilla is in the shallows at Duck Hollow, another a nearby fishing spot.

Despite its man-made origin Panther Hollow Lake is passing through the normal life cycle of a natural lake and is now doing its best to turn into a swamp and ultimately a meadow.

If we want an artificial lake or pond in a place where nature wants a meadow, we will have to spend a lot of money to make it that way and a lot of money over and over again to keep it that way. Money is tight, even for basic things … so that’s why Panther Hollow Lake is the way it is for now.

Read more about Panther Hollow lake at What’s Wrong With Panther Hollow Lake?