Wednesday, March 22, 2017

One of the Worst of the Worst: Purple Loosestrife (PL)

A "sea of purple" -- loosestrife reigns supreme; a view from the main West Marsh, northwest taken some time in the early 1990s. (Larger pedaled, pink blooms in foreground are the native but still aggressive Hibiscus moscheutos).

Before I get too far into our woodland restoration, I think it makes sense to at least dip our toes into the marsh . . . This story is a classic tale of good intentions gone bad. 

Purple loosestrife (Lythrum salicaria) -- or PL, as it will be abbreviated here -- is native to Europe and Asia. The plant was first introduced from Great Britain to the northeastern United States and Canada in the early 1800s for its medicinal, decorative, and horticultural values, possibly by bee keepers. There’s no denying it, in isolation and out of context it’s a pretty plant.

As is so often the case, beyond intentional planting, purple loosestrife could have also been introduced through various seed sources such as ship ballast, livestock feed, and animal bedding. Soon after entry, it was entrenched and smoldering, preparing to spread like wildfire.

According to the USFWS, loosestrife is now perhaps the most prevalent invasive species in the United States, covering approximately 400,000 acres of federal land, including wetlands, marshes, pastures and riparian meadows. While most prevalent in the northeast and Great Lakes, it is has now swept into each of the lower 48 states except Florida (interestingly).

Click here to read up more on purple loosestrife. Check this out if you want to gain a better appreciation for how it really started to impact Lake Erie marshes. But essentially, the take home lesson is that purple loosestrife became an unwelcomed “guest” that spreads aggressively by underground stems (rhizomes) and can produce as many as a million seeds per plant. Even supposedly sterile strains of L. virgatum (still commonly available in the horticulture trade) will outcross with this plant and produce viable seeds.

By the 1980s, purple loosestrife had arrived in Bay View and was the dominant plant in area marshes – outcompeting a tremendous diversity of sedges, rushes, and other native emergent plants (even cattails) to become a memorable “sea of purple.” It shaded shallow open water environments, and in so doing, could even snuff out native submerged plants. 

Quite simply, it was a game-changer. And it was looking like it might mean a permanent change to the landscape. I’ll leave it to a future entry to explain the rest of the story . . .

ASIDE: I had to smile when I first did a Google Images search on “Bay View Marsh” and found the image above to be the fourth result. We knew when we were getting into this project that we were inheriting a history of invasive species, but I have to admit, seeing that familiar magenta directly tied to what we are now managing put a bit of a lump in my throat!