Stuckenia filiformis
Stuckenia filiformis subsp. occidentalis
fineleaf pondweed, slender-leaf pondweed, thread-leaf false pondweed, thread-leaf pondweed, western pondweed
potamot filiforme occidental, slender-leaf pondweed, western fineleaf pondweed, western pondweed
freely branching proximally, sparsely branching distally, subterete, (10–)20–60(–100) cm.
20–100 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.
stipules disintegrating with age, those on proximal portion of stem inflated;
blade inflated; 0.2–5 mm wide.
peduncles terminal, erect, filiform to slender, 2–10(–15) cm;
spikes cylindric to moniliform, 5–55 mm;
verticels 2–6(–9).
peduncles with flower and/or fruits adjacent or separated by less than 2 cm.
dark brown, obovoid, 2–3 × 1.5–2.4 mm;
beak inconspicuous.
often absent.
Stuckenia filiformis
Stuckenia filiformis subsp. occidentalis
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.)
In the Great Lakes region, the name Potamogeton [Stuckenia] vaginatus has often been misapplied to this taxon. The distribution of S. vaginatus is further to the north and west than the Great Lakes region, however. Stuckenia filiformis subsp. occidentaliis rarely produces fruit in the eastern portion of its range, while to the north and west it commonly fruits. This subspecies is very similar to Potamogeton rostratus Hagström ([the combination does not exist within the genus Stuckenia)] of Asia and may prove to be the same taxon. Both grow in similar habitats. The proximal stipules are much enlarged and inflated, and the leaves are generally wider than the other subspecies.
(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 |
BC
OR
WA
CalFlora
Flora NW
Go Botany
MI Flora
MN Wildflowers
PNW Herbaria
WildflowerSearch
iNaturalist
USDA Plants Database
