Invasive Spotlight: Curly Leaf Pondweed

What is it?

Curly-leaf pondweed is a non native, invasive species. Growing up through the water column, it can grow in depths up to 10 feet deep. By out competing other native species it creates a thick mat of vegetation preventing recreation and reducing habitat for fish and other native plants.

How do you identify it?

Curly leaf pondweed is identified by its semi-transparent leaves, wavy leaf edges, and semi serrated texture. Leaf arrangement on the stem is alternating, with two opposite leaves never arriving from the same growth point. Like many invasives it is the first weed to start growing in the pond, though its growing season typically extinguishes in mid summer.

How does it spread?

Curly leaf pondweed was introduced through the aquarium and garden pond trade industry. It commonly spreads from uncleaned boats, transported fish, and waterfowl.

How can it be controlled?

Mechanical control by raking the weeds from the water is only effective in the short term as plants will regrow from the leftover seeds and roots.

Chemical treatment for most pondweeds will be endothall (contact) or fluridone (systemic). Endothall is formulated in a couple different ways; dipotassium salt of endothall is much more benign to fishes. Some newer herbicides will also be effective on the pondweeds, but they’re likely more expensive. Fluridone will be better suited to whole-water treatments. The contact herbicides would be better for spot treatments to leave beneficial coverage by select native plants less scathed.

Biological control comes in the form of grass carp, though success can vary from pond to pond. Refer to the following Ohio State University Extension factsheets for more information.