I’ve driven passed it a million times and so have you. When you’re going west on Route 50, just before you get to the Washington Beltway, there’s this swampy body of water off to the right. I’ve always wondered about that and finally, just this past week, decided to explore. I found it on Google Earth, and when I saw the name, Folly Branch, I knew I just had to see it in person.

Google Earth, incidentally, is a wonderful mapping resource. You can zoom in on any point on the planet in astonishing detail. I once traced the Nile to its source. It was easy. It would have saved Dr. David Livingstone no end of trouble. This time, I traced the Folly Branch from where it begins somewhere in the suburbs between Greenbelt and Bowie, down past Route 50 to where it joins the Western Branch, and on to where the Western Branch meets the Patuxent River in a marsh south of Upper Marlboro.

Now I just had to figure out how to find access to the Folly Branch. Searching several different apps and maps, I discovered the Folly Branch Trail, which is either in Seabrook, Lanham or Glenn Dale and either within the Folly Branch Stream Valley Park or Glenn Dale Park, depending on which particular app or map you consult. I came to the conclusion that the stream got its name from the colonist who first tried to find it, if you define the word folly as a fool’s errand.

Louise points out the beaver dam visible from the foot bridge. (Jeff Holland)

Last Sunday, I jumped in the car with my two-legged companion, Louise White, in the passenger seat and our four-legged companion, Millie the rescue retriever, on her rug in the back, and drove down Route 50 to see if we were on such an errand or not. Following the GPS, we exited Route 50 onto Martin Luther King Jr. Highway and turned onto Forbes Boulevard. It took about a half-hour to get there from our home in Annapolis.

You can start walking the trail at either end of Forbes Boulevard, but we decided to begin at the middle, where a conspicuous crosswalk marks where the trail crosses the road. There’s no parking lot, but plenty of room to park along the edge of the road. The trail on the west side of the road is fairly truncated and leads past a settling pond where a flock of resident Canada geese eyed Millie with alarm.

The stream flowed the color of a Starbuck’s Caramel Macchiato from the recent heavy rains. (Jeff Holland)

The trail on the east side of the road leads into a forest of loblolly pines and then comes to a T intersection where the main trail runs north and south a mile or so in each direction. The trails are all paved and relatively flat, so it’s an easy hike or bike ride. We crossed paths with a couple of joggers, but mainly had the whole park to ourselves.

We took the path to the right and headed down a gentle slope to the river bottom, where hardwoods like sweet gums, red maples, post oaks, river birches and other water-loving trees mixed with the pines. A long foot bridge crossed the stream, which was running the color of a Starbuck’s Caramel Macchiato from the recent heavy rains.

Beavers dammed this section of the stream (Jeff Holland)

The view of Folly Branch from the bridge was well worth the effort to find it. Upstream, a low beaver dam blocked the flow and formed a broad pond behind it. Someone had installed a 6-inch corrugated drainpipe in the middle, allowing the muddy water to flow underneath the dam. Looking more closely to one side of the stream, we could see a rivulet seeping through the mud and sticks that make up the dam. While the water flowing through the pipe was murky with suspended silt, the water filtered by the dam was clear as new moonshine in a Mason jar.

Before Capt. John Smith showed up on these shores in 1607, there were many such beaver dams everywhere, filtering every drop of rainwater before it ran downstream into the Chesapeake Bay. The first industry the colonists engaged in — way before they figured out how to chop down all the trees to open up fields to grow tobacco — was to slaughter all the beavers so they could sell their pelts to make fancy hats for English gentlemen. It’s taken us 400 years to start to repair all that damage. But I’ll leave the pontificating up to another columnist in this paper, who does a much better job of it than me.

The trail on the far end of the bridge took a turn that left us befuddled, but fortunately a young woman who lived nearby came walking along with her little dog to give us directions. We were on the main trail heading south and would eventually wind up at the end of the path where Forbes Boulevard meets MLK Jr. Highway.

A sea of native cattails provides habitat for beavers, muskrats and other critters. (Jeff Holland)

The trail followed the flow of the stream, which broadened at one point. On the maps, this area was an open lake. It might have been that at one time, but now it was one vast expanse of native cattails. I was relieved to see no trace of the invasive phragmite reeds. Cattails may be choking the waterway, but at least they provide food and shelter for beavers, muskrats and other critters.

In fact, the whole plant is not just edible, but downright useful. Native Americans would pick the tender shoots and eat them cooked or raw. The characteristic bushy bits at the top are dark brown when they’re mature, but when they’re still green, these flower stalks would be boiled and eaten like corn on the cob. The Native Americans would weave cattail leaves and stalks into mats and baskets and line moccasins with cattail down. The roots and pollen served as medicinal herbs. And even now, while the reeds are growing, they’re absorbing excess nutrients from the stormwater that could pollute the river and capturing carbon dioxide that pollutes the air.

Louise used her binoculars to follow the flight of a belted kingfisher — one of her favorite birds — as it flicked back and forth across the stream, snatching up bugs. We heard a pileated woodpecker cackling off in the woods. I was disappointed that we didn’t see any beavers, since their work there was so extensive. We marveled at the fact that we were in the midst of such urban sprawl yet surrounded by such a unique bit of natural beauty. Maybe this expedition wasn’t such a folly after all.

Louise follows a belted kingfisher snagging bugs over the stream. (Jeff Holland)

Forbes Boulevard, near Bartley Way

No admission. No toilet facilities. Pack out all trash.

Open sunrise to sunset. Polite dogs on leashes are welcome.