Stuckenia filiformis (Pers.) Boerner
Northern Slender Pondweed
Habitat: Alkaline ponds and stream. [Open water (non-forested, wetland)]
Range: Greenland to Alaska, south to northern New England, Michigan, New York, and west to Colorado, New Mexico, Texas, and Utah.
Aids to Identification: Stuckenia filiformis is a pondweed with no floating leaves and linear, submersed leaves. Stipules are fused to leaf sheaths for at least 1 cm. Leaves are 0.2-0.8 mm wide, not lobed at base, tips blunt, obtuse, or notched (rarely apiculate). Plants are 10-30 cm long, with tightly clasping, persistent leaf sheaths..
Ecological characteristics: In Maine, this species is mostly restricted to sheltered areas in ponds or slow moving streams with high pH in Aroostook county. Sites where these plants have been found range in pH from 7.3 to 9.1.
Phenology: A perennial; fruits (often helpful for identification) ripen in August - September.
Synonyms: Previously tracked in Maine as two infraspecific taxa, a more robust plant with broader leaves and sterile fruits more commonly found in moving water (ssp. occidentalis) and a narrower-leaved plant with fertile fruits more commonly found in still and slow-moving water (ssp. alpina). Subspecies occidentalis has been determined to be a hybrid between S. filiformis and S. pectinata.
Synonyms at the species level include Coleogeton filiformis (Pers.) D. Les & R. Haynes ssp. alpinus (Blytt) D. Les & R. Haynes; Coleogeton filiformis (Pers.) D. Les & R. Haynes ssp. occidentalis (J.W. Robbins) D.H. Les & R. Haynes; Potamogeton filiformis Pers. var. alpinus (Blytt) Aschers. & Graebn.; Potamageton filiformis Pers. var. borealis (Raf.) St. John; Potomageton filiformis Pers. var. macounii Morong; Potamogeton filiformis Pers. var. occidentalis (J.W. Robbins) Morong; Stuckenia filiformis (Pers.) Börner ssp. alpina (Blytt) Haynes, D.H. Les, & M. Kral; Stuckenia filiformis (Pers.) Börner ssp. occidentalis (J.W. Robbins) Haynes, D.H. Les, & M. Kral.
Known Distribution in Maine: This rare plant has been documented from a total of 13 town(s) in the following county(ies): Aroostook.
Reason(s) for rarity: Southern limit of range; suitable habitat naturally scarce.
Conservation considerations: Maintain hydrologic integrity of its alkaline water habitat.