Excerpts from Jim Conrad's
Naturalist Newsletter

Curled Pondweed, POTAMOGETON CRISPUS

from the the May 24, 2009 Newsletter, issued from the Siskiyou Mountains west of Grants Pass, Oregon:
CURLED PONDWEED

When I arrived here a little over a month ago, in the fairly clear waters of the little pond above my trailer, I saw ribbons of an aquatic plant rising toward the water's surface with distinctive, wavy- margined leaves. Over the weeks I've watched the ribbons rapidly grow longer until now they've reached the water's surface and form a thick tangle of ropy stems just below the surface. You can see some sprigs above.

This is Curled Pondweed, POTAMOGETON CRISPUS. I read that Curled Pondweed rarely propagates with seeds. Mostly it reproduces by stem fragmentation and by the production of hard, burr-like items called "turions." In the last picture a turion lies atop my middle fingers, above the sprig lying across my hand. Basically turions are compacted, hardened stem-tips. A close-up of one can be seen below:

Turion of Curled Pondweed, POTAMOGETON CRISPUS

When Curled Pondweeds finish flowering and producing turions in late spring and early summer the plants disintegrate -- rot away -- leaving only fruits and turions. The turions germinate in late summer or fall, the plants overwinter as small plants just a few inches long, even under ice, and then growth continues when the water warms in spring.

Despite many plants producing turions now, currently many plants also are issuing slender, whitish, inch- long flower spikes above the water. A close-up showing a spike with four or five blossoms can be seen below:

Curled Pondweed, POTAMOGETON CRISPUS, flowers.

In that picture each globular mass is a flower. The calyx and corolla, or perianth, have been reduced to one or two brown scales arising beneath each blossom. The whitish objects are anthers filled with pollen. Four two-celled anthers crowd around each ovary, the future fruit, so you can't see the ovary, but the pink styles and stigmas atop the ovaries are clearly visible.

Curled Pondweed is an invasive plant introduced from Eurasia in the mid 1800s and now found all across North America as well as other parts of the world. Often the species causes serious problems clogging waterways. In our pond, however, little fish looking for shelter from big fish love it, and big bullfrog tadpoles can be seen resting suspended in its tangles just below the water's surface.