Non-Native to Chesapeake Bay; non-invasive in tidal waters, invasive in non-tidal waters

• Family - Potamogetonaceae
   
• Distribution - Curly pondweed grows in fresh non-tidal to slightly brackish tidal waters. Curly pondweed is thought to have been introduced from Europe in mid-1800's; today it has worldwide distribution and is widely distributed in streams, rivers and reservoirs of the Chesapeake Bay.
   
• Recognition - Leaves are 3 cm to 10 cm (1 ¼ in to 4 in) long, broad, linear and finely toothed, with undulated (curly) margins. Leaves are arranged alternately or slightly opposite on flattened, branched stems. Roots and rhizomes are shallow, and not as extensive as in other bay grasses. Vegetative buds sprout in the fall and the winter form of the plant develops with blue-green leaves that are more flattened. In spring, the spring/summer form appears with reddish-brown leaves that are wider and curlier. Flowering occurs in late spring or early summer and the plants begin to die-off in midsummer after the vegetative buds are produced. The buds remain dormant until fall, when the cycle is repeated.
   
• Ecological Significance - Curly pondweed is an introduced species that is widespread throughout the U.S. Curly pondweed has a three-stage life cycle and distinctly different winter and summer forms. Curly pondweed can be particularly invasive when it occurs in lakes and reservoirs (non-tidal waters).
   
• Similar Species - Curly pondweed may resemble young shoots of redhead grass (Potamogeton perfoliatus).
   
• Reproduction - Plants reproduce through extension of rhizomes, development of burr-like asexual structures near stem tips, and by seed development from flowers that float at water surface atop spikes. The curly pondweed life-cycle has a three-stages: winter form, spring/summer form, and dormant vegetative (asexual) bud.