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.

20170710_161734

Water lettuce survived the Pennsylvania winter in the Lehigh Canal. 10 July 2017.

20170710_161837

Water hyacinth also survived the Pennsylvania winter in the Lehigh Canal. 10 July 2017.

20170710_162915

Larger clump of water lettuce in the middle of the canal. 10 July 2017.

20170710_162349

Only a little bigger than the duckweed, you can see the light-green colored water lettuce in this image. Given the small size, I suspect it came back from seed. 10 July 2017.

Advertisements

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 , , , , , , . Bookmark the permalink. Leave a comment.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: