Curly pondweed (Potamogeton crispus)

Curly pondweed Common Names: Curly-leaved pondweed, pondweed

Description: This species is listed as a restricted noxious weed by the Michigan Department of Agriculture. Begins growing in early spring, dies back completely by mid summer after blooming; inhibits growth of native plants; midsummer die-back results in masses of dead vegetation, increase in phosphorus levels and potential algal blooms.

Habit: Submergent aquatic perennial; ranges from 30-80 cm (1-2.5 ft) in length, forms dense mats.

Leaves: Submerged, alternate, oblong, up to 10 cm (~4 in) long and 1 cm (0.4 in) wide, rounded at the tip; slightly clasping the stem at the base, wavy leaf margins with fine teeth.

Stems: Compressed, four-angled, few branches, up to 80 cm (31 in) long and 1-2 mm wide.

Flowers: Found on dense cylindrical spikes that rise above the water for wind pollination; bloom in late spring/early summer.

Fruit and seeds: Small (4-6 mm long), brown, with a pointed beak.

Habitat: Found in shallow to deep water of lakes and rivers; pollution-tolerant; prefers alkaline, nutrient-rich waters.

Reproduction: Vegetatively by spindle-shaped turions (winter buds that form at leaf axils and stem tips); turions lie dormant during summer, germinate in fall; also spreads by fragmentation; seeds probably not viable.

Similar species: Curly pondweed is similar to many other Potamogeton species but it is the only one with curly leaf edges.

Monitoring and rapid response: Monitor water bodies for new colonies in spring. Public education is critical. Raking/cutting at sediment surface in spring can prevent propagule formation - remove all fragments. Herbicide applications at low rates in early spring provide effective control; plants die back completely by late spring or early summer so later application ineffective; where water levels can be manipulated, fall drawdown may kill turions. Permits are usually required for herbicide use in water bodies and wetlands. For information see MDEQs Aquatic Nuisance Control website at: www.michigan.gov/deqinlandlakes.

Credits: The Michigan Natural Features Inventory (MNFI) has partnered with MISIN to provide the information in this fact sheet. Species images and/or information were used with permission from "A Field Identification Guide to Invasive Plants in Michigan's Natural Communities" and "A Field Guide to Invasive Plants of Aquatic and Wetland Habitats for Michigan.


Common Name:

Curly pondweed

Scientific Name:

Potamogeton crispus

Family:

Potamogetonaceae
(Pondweed)

Duration:

Perennial

Habit:

Aquatics

USDA Symbol:

POCR3