Species: Potamogeton strictifolius Oakes

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Potamogeton strictifolius Oakes

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TAXONOMY

Family:

Potamogetonaceae

Genus:

Potamogeton

Species Synonyms:

Potamogeton longiligulatus Fern.
Potamogeton pusillus var. rutiloides (Fern.) Boivin
Potamogeton rutilus auct. non Wolfgang
Potamogeton strictifolius var. rutiloides Fern.
Potamogeton strictifolius var. typicus Fern.

Common Names:

narrowleaf pondweed
straight-leaved pondweed

DISTRIBUTION

Canada:

east-central Yukon, south to central Alberta, south-central Saskatchewan, Manitoba – Ontario – Quebec

Saskatchewan:

southern to central Saskatchewan; Cypress Hills – Cabri Lake – Regina – Saskatoon – Candle Lake

Ecoregion:

Cypress Upland, Mixed Grassland, Moist Mixed Grassland, Boreal Transition, Mid-Boreal Upland

HABITAT

Saskatchewan:

in shallow water of protected lake bays, ponds, and slow streams

Associated Species:

Schoenoplectus acutus var. acutus

RARITY STATUS

Provincial Status According
to Harms (2003):

Threatened

Nature Conservancy Status:

G5 S2

Saskatchewan Species at
Risk Status:

None

COSEWIC Status:

None

Potamogeton strictifolius is threatened because it is rare or uncommon in Saskatchewan. No immediate threats are known but may occur in the future.

SPECIES DESCRIPTION

Height:

25 – 90 cm

Roots:

roots fibrous; rhizomes absent

Stems:

terete, slender, lacking spots, glands at nodes (if present) greenish to brown or gold; turions terminal or lateral, common

Leaves:

submersed, spirally arranged, rigid, sessile, 1.2 – 6.5 cm long, 0.6 – 2 mm wide, linear, base not lobed or clasping, tip tapered, lacunae absent, veins 3 – 5, green, margin entire; stipules disintegrating, connate, free from blade, white, fibrous, shredding at tip

Inflorescence:

spikes uniform, 6 – 13 mm long, emersed, slender; peduncles uniform, terminal, 1 – 4.5 cm, erect

Flowers:

small, green; tepals 4; stamens 4; carpels 4

Fruits:

sessile, 2 – 3 mm long, green-brown, not keeled

POTAMOGETON KEY FOR SPECIES FOUND IN SASKATCHEWAN

1 Stipular sheaths of submersed leaves adnate to base of leaf blade; leaf margins cartilaginous	P. robbinsii
1 Stipular sheaths of submersed leaves free from base of leaf blade; leaf margins not cartilaginous	2

2 Submersed leaves oblong to lanceolate to nearly orbicular	3
2 Submersed leaves ribbon-like or thread-like	9

3 Leaf margins conspicuously serrate and undulate; turions present	P. crispus
3 Leaf margins entire or undulate; turions absent	4

4 Submersed leaves clasping; floating leaves absent	5
4 Submersed leaves not clasping, may be petiolate; floating leaves present or absent	6

5 Stipules persistent; rhizome with rusty spots	P. praelongus
5 Stipules shredding into fibres; rhizome not obviously spotted	P. richardsonii

6 Floating leaf blade rounded to cordate; stem rusty or black-spotted; submersed leaves arcuate	P. amplifolius
6 Floating leaf blade cuneate or rounded; stems without spots; submersed leaves not arcuate	7

7 Submersed leaves petiolate	P. nodosus
7 Submersed leaves sessile	8

8 Fruits plump, pedicellate; submersed leaf blade 7 – 9-veined	P. alpinus
8 Fruits compressed, sessile; submersed leaf blade 3 – 19-veined	P. gramineus

9 Floating leaves present on at least some plants in a population
9 Floating leaves absent

10 Lacunae present and prominent; submersed leaves with distinction between blade and petiole; leaves dimorphic, the floating ones long-petioled and wider than the submersed ones	P. epihydrus
10 Lacunae absent or not prominent; submersed leaves phyllodial; leaves uniform, no distinction between the floating and submersed leaves	P. natans

11 Nodes without glands	12
11 Nodes glandular	13

12 Leaves 15 – 35-veined, greater than 2 mm wide; stem wing-flattened	P. zosteriformis
12 Leaves 3 – 5-veined, less than 2 mm wide; stem not wing-flattened	P. foliosus ssp. foliosus

13 Stipules fibrous, whitish	14
13 Stipules not fibrous, green, brown or whitish	15

14 Leaf apex acute to apiculate, leaves thin, 5 – 7-nerved; peduncles at most 5 cm long	P. friesii
14 Leaf apex bristle-tipped; leaves firm, 3-nerved; peduncles to 9 cm long	P. strictifolius

15 Fruits 2.5 – 3.5 mm long	P. obtusifolius
15 Fruits 1.5 – 2 mm long	16

16 Mature fruits obovoid; peduncles 1 – 3 per plant; leaf blade with less than 2 rows of lacunae along midrib	P. pusillus ssp. pusillus
16 Mature fruits widest at the middle; peduncles more than 3 per plant; leaf blade with 1 – 5 rows of lacunae along midrib	P. pusillus ssp. tenuissimus