Curly pondweed (Potamogeton crispus)

Identification:

This is the only species of pondweeds in North America with serrate leaves and consequently it is easily recognized.Curly pondweed gets its name from the wavy margins on the sides of its leaves. Leaves are dark green with a reddish hue and have small teeth along the margins. Plants may grow up to 2 meters long. Rhizomes absent. Cauline stems flattened, without spots, to 100 cm; nodal glands absent. Turions common, axillary or terminal, 1.5-3 ´ ca. 2 cm, hard; leaves ± 2-ranked; outer leaves 1-4 per side, base not corrugate, apex rounded; inner leaves rolled into linear, terete structure, oriented parallel to outer leaves. Leaves submersed, ± spirally arranged, sessile, lax; stipules persistent to deliquescent, inconspicuous, convolute, free from blade, brownish, not ligulate, to 0.5 cm, not fibrous, not shredding at tip, apex obtuse; blade light to dark green, linear, not arcuate, 1.2-9 cm ´ 4-10 mm, base obtuse to rounded, without basal lobes, not clasping to nearly clasping, margins conspicuously serrate, not crispate, apex not hoodlike, round to round-acute, lacunae in 2-5 rows each side of midrib; veins 3-5. Inflorescences unbranched, emersed; peduncles not dimorphic, terminal or rarely axillary, erect to ascending, cylindric, 2.5-4 cm; spikes not dimorphic, cylindric, 10-15 mm. Fruits sessile, red to reddish brown, obovoid, turgid to slightly concave, not abaxially or laterally keeled, 6 ´ 2.5 mm; beak apically recurved, 2-3 mm; sides without basal tubercles; embryo with 1 full spiral. 2n = 52 (Europe).

Ecology:

Flowering spring-summer. Quiet waters, especially brackish, alkaline, or eutrophic waters of ponds, lakes, and streams; typically <3m, maximum depth 12m. May spread by re-rooting of small plant fragments.

Life history of Potamogeton crispus is unusual as it flowers and fruits in late spring and early summer, at which time it also produces turions. The plants decay shortly after those structures develop, leaving only fruits and turions, which survive the summer. No one has observed any seed germination, but the turions (referred to as dormant apices) germinate in late summer or fall, and the plants overwinter as small plants only a few cm centimeters in size, even under the ice in northern climates. Growth then continues as the water begins warming in the spring.

Curly leaf pondweed is important in spring as a provider of cover for small aquatic animals which serve as food for migrating waterfowl and as a spawning substrate for fish because it is one of the most abundant macrophytes from April toJune.

Distribution Map:

Means of Introduction:

The species has since spread across much of the United States, presumably by migrating waterfowl, intentional planting for waterfowl and wildlife habitat, and possibly even as a contaminant in water used to transport fishes and fish eggs to hatcheries. P. crispus can also spread by plant fragments attached to boats and equipment that are not

properly cleaned.

Status:

Established in all of the continental United States except Maine and South Carolina and Ontario in Canada and New Zealand.

Impact of Introduction:

Due to excessive growth, this species sometimes becomes a pest in waterways, lakes and reservoirs. The Eurasian pondweed competes with native plantlife and sometimes displaces the native plantlife. Dense colonies of curly pondweed can restrict access to docks and sport fishing areas during spring and early summer months. It may interfer with late spring and early summer recreation due to the formation of dense mats and an increase in phosphorus concentrations causing an increase in algae blooms and a pile up of dying P. crispus along the shore, both due to its mid-summer die back.

P. crispus tends to increase oxygen levels at day-time and produce substantial organic material in aquatic environments. This pondweed shelters small fish and aquatic insects that provide food for larger fish and amphibians. It is a fast growing plant in need of constant checking to make sure it does not overrun ponds, pools or canals. Because populations of curly pondweed usually decline during the summer months, it does not directly compete with many of the native submersed species.Curly-leaf pondweed is considered a nuisance by many, but has received very little attention after the accidental introduction of Eurasian watermilfoil and other invasive species.

Sourced From: http://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=1134