Stuckenia filiformis
Stuckenia pectinata
fineleaf pondweed, slender-leaf pondweed, thread-leaf false pondweed, thread-leaf pondweed, western pondweed
fennel pondweed, fennel-leaf pondweed, potamot pectine, sago false pondweed, sago-pondweed
freely branching proximally, sparsely branching distally, subterete, (10–)20–60(–100) cm.
branched, especially distally, terete to slightly compressed, to 75 cm.
length and width of those on main stem only slightly larger than those on branches;
stipules with stipular sheaths often inflated on proximal portion of stem, 1–4(–9.5) cm, summit of midstem stipules tight to stem, ca. ± same width as stem, ligule 2–20 mm, distinct, especially on distal stipules;
blade filiform or slenderly linear, 1–15 cm × 0.2–2(–3.7) mm, apex notched, blunt, or short-apiculate;
veins 1–3.
those of main stem only slightly larger than those of branches;
stipules with stipular sheaths not inflated, 0.8–1.1 cm, ligule 0.8 mm;
blade linear, 5.6–9.2 cm × 0.2–1 mm, apex acute to mucronate or apiculate;
veins 1–3.
peduncles terminal, erect, filiform to slender, 2–10(–15) cm;
spikes cylindric to moniliform, 5–55 mm;
verticels 2–6(–9).
peduncles terminal or axillary, erect to ascending, cylindric, 4.5–11.4 cm;
spikes moniliform to cylindric, 14–22 mm;
verticels 3–5.
dark brown, obovoid, 2–3 × 1.5–2.4 mm;
beak inconspicuous.
yellow-brown to brown, oblanceoloid, 3.8–4 × 2.5–3.1 mm;
beak toward abaxial margin, erect, 0.5–1.1 mm.
= 78.
Stuckenia filiformis
Stuckenia pectinata
Three distinct subspecies seemingly apparently occur in North America. They are separated mainly by the size of the plants and the peduncle characteristics. Stuckenia filiformis subsp. occidentalis typically grows in cold deep water, standing or with a strong current. This variety tends to become robust and is easily confused with Stuckenia vaginata and S. striata. Stuckenia filiformis subsp. alpina is a much smaller plant typically growing in standing waters. Stuckenia filiformis subsp. filiformis is restricted to the far north. In the intermountain region of western United States is a more robust form that is quite similar to S. filiformis subsp. alpina but although it has previously been recognized as Potamogeton [Stuckenia] filiformis var. macounii Morong (J. L. Reveal 1977b).
Subspecies ca. 5 (3 in the flora).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
No specimens have been seen from Delaware, but the species is to be expected there.
The sago-pondweed is among the most important species as food for waterfowl (E. Moore 1913). The species reproduces vegetatively by underground tubers and is spread by various duck species, especially canvas backs. In a study of food for ducks, a population of canvas backs was observed feeding in aquatic vegetation comprised of several genera, including sago-pondweed. When the stomach contents were examined, they were found to contain essentially 100% tubers of sago-pondweed (E. Moore 1913).
Two hybrids with this species as a putative parent have been described under the genus Potamogeton. These are P. pectinatus × P. vaginatus (= P. × bottnicus Hagström) and P. filiformis × P. pectinatus (= P. × suecicus K. Richter).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Plants 20–100 cm; stipules on proximal portion of stem inflated, disintegrating with age; fruits often absent. | subsp. occidentalis |
1. Plants 10–30 cm; stipules on proximal portion of stem tightly clasping or slightly enlarged, persistent; fruits common. | → 2 |
2. Peduncles Peduncles with flowers and/or fruits 4 cm or more apart; leaves 0.2–0.5 mm wide. | subsp. Filiformis |
2. Peduncles with flowers and/or fruits less than 4 cm apart; leaves to 1 mm widee. | subsp. alpina |
- Local floras:
BC, 
CA, 
OR, 
WA - Local Web sites: CalFlora, CalPhotos,
Flora NW, 
Go Botany, 
IL Wildflowers, 
KS Wildflowers, 
LA Plants, 
MD Biodiversity, 
MI Flora, 
MN Wildflowers, 
MO Plants, 
PNW Herbaria 
WildflowerSearch
iNaturalist (observations)
USDA Plants Database- LBJ Wildflower Center
- SEINet
- Plants of the World Online
- Encyclopedia of Life
- Wikipedia
- Google Image Search
