Invasion confirmed. Water lettuce and water hyacinth overwintering in Pennsylvania.
Last September, two invasive aquatic plants, water lettuce (Pistia stratiotes) and water hyacinth (Eichhornia crassipes), were discovered in the Lehigh Canal in Bethlehem PA. Both species are floating plants, like duckweeds but much larger, and they often grow in dense mats in tropical and subtropical regions. Although this was the first confirmed occurrence in natural habitat within Pennsylvania, both species are sensitive to freezing temperatures so they have not not been regarded as major threats in the Northeast. A description of the discovery of these populations and some background on the species, including a discussion of recent work suggesting that the overwintering potential may be greater than previously thought, can be found in my post from last year (New invaders in the Lehigh Valley? Or Just Summer Visitors?).
The discovery last year prompted several questions. In particular, are these populations really persisting from year-to-year and therefore surviving freezing temperatures? I suspected that they were introduced last summer from someone’s pond and that they would not survive the winter. However, the winter was mild and the recent discovery of some overwintering populations in the lower Great Lakes gave me pause. I road my bike along the canal towpath last week to have a look.
I was wrong. Both species have overwintered. A harbinger of things to come? Below are some pictures, and I’ll update this post with more later in the summer.
Posted on July 18, 2017, in Conservation & Biodiversity (EES-28), Ecology (EES-152), Fieldwork, Personal / Just for Fun, Research, Teaching, Wetland ecology (EES-386) and tagged Ecology, invasive species, Nature, Plants, water hyacinth, water lettuce, Wetlands. Bookmark the permalink. Leave a comment.