Curly Leaf Pondweed (Potamogeton crispus L.)

Family: Potamogetonaceae  

(November 2004)

Description and Variation: 

Curly-leaf pondweeds grows entirely underwater except for the flower stalk which rises above the water. Curly leaf pondweed has distinctly wavy-edged, crispy olive-green to reddish-brown leaves. It usually grows early in spring and dies back in summer. Similar plants include Flat-stem pondweed. The leaves of flat-stem pondweed are long and narrow with smooth edges and the sharp-edged stem is flat and about the same width as the leaves.

Leaf: Alternate, all submersed, no leaf stalks. Curly leaf: oblong, stiff, translucent leaves (4-10 cm long, 5-10 mm wide) have distinctly wavy edges with fine teeth and 3 main veins. Sheaths (stipules) up to 1 cm long are free of the leaf base and disintegrate with age. Flat-stem: smooth-edged leaves (5-20 cm long, 2-5 mm wide) have many veins. Sheaths (stipules) 2-6 cm long are free of the leaf base and become fibrous with age.

Stem: Curly leaf: branched, up to 90 cm long, somewhat flattened. Flat-stem: generally few branched, up to 2 m long, 0.7-4 mm wide, flattened, with sharp edges.

Flower: Tiny, with 4 petal-like lobes. Curly leaf: in spikes 1-3 cm long on stalks up to 7 cm long. Flat-stem: in spikes up to 3 cm long on stalks up to 10 cm long. 

Fruit: Seed-like achene. Curly leaf: 4-6 mm long including 2-3 mm beak, back ridged. Flat-stem: approximately 5 mm long, sharp ridge on back, short beak.

Economic Importance: 

Detrimental: Curly leaf pondweed (Potamogeton crispus) is an invasive plant that forms surface mats that interfere with aquatic recreation. Dense colonies of curly pondweed can restrict access to docks and sport fishing areas during spring and early summer months. Curly-leaf pondweed has been noted as one of the most severe nuisance aquatic plants in the Midwest only out ranked Eurasian Watermillfoil. Because populations of curly pondweed usually decline during the summer months, it does not directly compete with many of the native submersed species. Cost for control and can range in the Millions per lake.

Beneficial:  none known

 Habitat: Curly leaf: shallow to deep still or flowing water, tolerant of disturbance. Flat-stem: ponds, lakes, 1-2.5 m deep. Curly leaf: nearly worldwide. Flat-stem: widespread in temperate North America; found throughout Washington.

Geographic Distribution:  Native to Eurasia, Africa, and Australia, this species has been found in most of the United States since 1950

Washington Distribution:  Found in

History: Curly pondweed, Potamogeton crispus L., is native to Eurasia and apparently was introduced into the United States in the mid 1800’s (Stuckey 1979). Prior to 1900, the distribution of P. crispus was the northeastern United States. By 1930 curly pondweed had spread westward to several states of the Great Lakes region. The species has since spread across much of the United States, presumably by migratingwaterfowl, intentional planting for waterfowl and wildlife habitat, and possibly even as acontaminant in water used to transport fishes and fish eggs to hatcheries (Stuckey 1979).

Growth and Development:  Curly pondweed perennial, rooted, submersed aquatic vascular plant  that produces seed, but the importance of seed in the spread and maintenance of populations is unknown (Stuckey 1979) and is assumed to be less important than turions (Sastroutomo 1981). In most portions of its range, Potamogeton crispus typically reaches peak biomass in the late spring or early summer months, forms turions, then declines and "survives" the warmer months in a dormant state (i.e., as a turion) (Cypert 1967, Stuckey 1979, Sastroutomo 1981, Tobiessen and Snow 1984, Nichols and Shaw 1986). As water temperatures cool during the late summer or fall months, the turions germinate, grow through the winter months with the plants reaching peak biomass in the spring before most other submersed macrophytes begin their growth cycle. Once established, the plants regrow and form colonies from rhizomes.

Curly leaf pondweed has a unique life cycle which gives it competitive advantages over many native aquatic plants. Unlike most native plants, curly leaf pondweed may be in a photosynthetically active state even under thick ice and snow cover (Wehrmeister and Stuckey, 1978). Therefore, it is often the first plant to appear after ice out. By late spring it can form dense mats which may interfere with recreation and limit the growth of native aquatic plants (Catling and Dobson, 1985). Curly leaf plants usually die back in early summer in response to increasing water temperatures, but they first form vegetative propagules called turions (hardened stem tips). New plants sprout from turions in the fall (Catling and Dobson, 1985).

Control:

Biological - Grass carp will seldom control aquatic vegetation the first year they are stocked.  They will consume curly-leaf pondweed.  Grass carp stocking rates to control curly-leaf pondweed are usually in the range of 7 to 15 per surface acre.

References: 

Cypert, E. 1967. The curly-leaved pondweed problem at Reelfoot Lake. Journal of the Tennessee Academy of Science 42:10-11.

Nichols, S. A. and B. H. Shaw. 1986. Ecological life histories of the three aquatic nuisance plants, Myriophyllum spicatum, Potamogeton crispus, and Elodea canadensis. Hydrobiologia 131: 3-21.

Sastroutomo, S. S. 1981. Turion formation, dormancy and germination of curly pondweed, Potamogeton crispus L. Aquatic Botany 10: 161-173.

Stuckey, R. L. 1979. Distributional history of Potamogeton crispus (curly pondweed) in North America. Bartonia 46: 22-42.

Tobiessen, P. and P. D. Snow. 1984. Temperature and light effects on the growth of Potamogeton crispus in Collins Lake, New York State. Canadian Journal of Botany 62: 2822-2826.

Rationale for Listing: Dense colonies of curly pondweed can restrict access to docks and sport fishing areas during spring and early summer months.