''Potamogeton crispus'', the crisp-leaved pondweed, curly pondweed, curly-leaf pondweed or curled pondweed, is a species of

aquatic plant Aquatic plants are plants that have adapted to living in aquatic environments ( saltwater or freshwater). They are also referred to as hydrophytes or macrophytes to distinguish them from algae and other microphytes. A macrophyte is a plant that ...

(hydrophyte) native to

Eurasia Eurasia (, ) is the largest continental area on Earth, comprising all of Europe and Asia. Primarily in the Northern and Eastern Hemispheres, it spans from the British Isles and the Iberian Peninsula in the west to the Japanese archipelag ...

but an

introduced species An introduced species, alien species, exotic species, adventive species, immigrant species, foreign species, non-indigenous species, or non-native species is a species living outside its native distributional range, but which has arrived there ...

and often a

noxious weed A noxious weed, harmful weed or injurious weed is a weed that has been designated by an agricultural or other governing authority as a plant that is injurious to agricultural or horticultural crops, natural habitats or ecosystems, or humans or li ...

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and th ...

Description

Curly-leaf pondweed is a rhizomatous perennial herb producing a flattened, branching stem up to a meter long. The submerged leaves are alternately arranged. The leaves are sessile, linear or oblong in shape, long and wide. The leaves may be bright green, olive green or (especially later in the season) fibrous and brownish and have noticeably serrated margins, a feature that distinguishes them from other pondweeds. The leaves usually have wavy edges but this is not always apparent, especially on new growth. Turions occur in leaf axils and at stem tips. The

inflorescence An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Morphologically, it is the modified part of the shoot of seed plants where flowers are forme ...

is a short spike of flowers emerging above the water surface. It flowers from May until October. Potamogeton crispus turion

The turions of the plant develop along with the fruits and germinate, leaving the newly sprouted plants to

overwinter Overwintering is the process by which some organisms pass through or wait out the winter season, or pass through that period of the year when "winter" conditions (cold or sub-zero temperatures, ice, snow, limited food supplies) make normal activi ...

. Although quite variable, ''P. crispus'' is usually a straightforward plant to identify. Hybrids with various other pondweeds are recorded, but these do not usually closely resemble ''P. crispus''. There are described hybrids with '' Potamogeton trichoides'' (''P''. × ''bennettii'' Fryer), '' P.perfoliatus'' (''P''. × ''cooperi'' (Fryer) Fryer), '' P. alpinus'' (''P''. × ''olivaceus'' Baagøe ex G.Fisch.), '' P.lucens'' (''P''. × ''cadburyae'' Dandy & G.Taylor), '' P. praelongus'' (''P''. × ''undulatus'' Wolgf.), ''P. ochreatus'' (''P''. × ''jacobsii'' Z.Kaplan, Fehrer & Hellq.) and ''P. friesii'' (''P''. × ''lintonii'' Fryer).

Distribution

''Potamogeton crispus'' is native to a wide range of countries in Asia (Afghanistan, Bangladesh, Bhutan, China, India, Indonesia (Sumatra), Japan, Kazakhstan, Korea, Kyrgyzstan, Laos, Mongolia, Myanmar, Nepal, Pakistan, Russia, Tajikistan, Thailand, Turkmenistan, Uzbekistan, Vietnam); Africa, the Middle East, Australia, and Europe. It has been introduced to the Americas and New Zealand.

Ecology

Curly pondweed is widespread and common across most of its native range, growing in standing and slow-flowing water including small ponds and ditches. It is strictly a lowland plant and requires fine substrates in standing or slow-flowing calcareous water. However, it is tolerant of significant nutrient pollution, and this has allowed it to persist in intensively farmed areas where more sensitive pondweeds have declined. Its production of both seed and turions makes it relatively resistant to disturbance such as dredging, in contrast to some of the larger broad-leaved pondweeds, although cutting down to the sediment surface in the early growing season may inhibit turion production. Potamogeton crispus Dorset

Environmental impact

This pondweed is considered an invasive species in much of North America. It was introduced to the

Great Lakes The Great Lakes, also called the Great Lakes of North America, are a series of large interconnected freshwater lakes in the mid-east region of North America that connect to the Atlantic Ocean via the Saint Lawrence River. There are five lakes ...

and inland lakes within that region. The plant thrives in conditions normally less habitable to native plant species. It is also able to survive beneath the surface of frozen waterways and resume its rapid vegetative growth before other water plants can regrow. It competes with native plant life and sometimes displaces it. Curly pondweed may clog waterways, inhibiting aquatic recreation, and is considered a nuisance in some areas. It has also been introduced to South America and New Zealand.

Cultivation

''Potamogeton crispus'' is sometimes cultivated as a pond plant, and generally speaking makes a good garden plant. Since it starts to die back rather early, it is probably a good idea to cut it back in July after it has flowered. In common with other pondweeds of this group it roots poorly from stem cuttings and is best propagated by division of the rhizomes or from turions. As it has proved invasive in some areas, curly pondweed should not be grown outside its native range.

References

External links

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CalPhotos Photo galleryGLANSIS Species FactSheet

Species Profile- Curly Pondweed (''Potamogeton crispus'')
National Invasive Species Information Center,

United States National Agricultural Library The United States National Agricultural Library (NAL) is one of the world's largest agricultural research libraries, and serves as a national library of the United States and as the library of the United States Department of Agriculture. Located ...

. Lists general information and resources for Curly Pondweed. {{Taxonbar, from=Q157863

crispus Flavius Julius Crispus (; 300 – 326) was the eldest son of the Roman emperor Constantine I, as well as his junior colleague ( ''caesar'') from March 317 until his execution by his father in 326. The grandson of the ''augustus'' Constantius ...

Freshwater plants