Species: Potamogeton strictifolius Oakes

comments | credits | copyright

Back to: Plants at Risk in Saskatchewan

Potamogeton strictifolius Oakes

Species Image Gallery
(opens in a new window)

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:

hardstem bulrush

RARITY STATUS

Provincial Status According
to Harms (2003):

Threatened

Nature Conservancy Status:

G5 S2

Saskatchewan Species at
Risk Status:

None

COSEWIC Status:

None

Narrowleaf pondweed 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:

round, slender, lacking spots, glands at nodes (if present) greenish to brown or gold; overwintering stems 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, air spaces absent, veins 3 – 5, green, margin entire; stipules disintegrating, fused, free from blade, white, fibrous, shredding at tip

Inflorescence:

spikes uniform, 6 – 13 mm long, emersed, slender; inflorescence stalks 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 boat-shaped

POTAMOGETON KEY FOR SPECIES FOUND IN SASKATCHEWAN

1 Stipular sheaths of submersed leaves fused 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 lance-shaped to nearly round	3
2 Submersed leaves ribbon-like or thread-like	9

3 Leaf margins conspicuously saw-toothed and wavy; overwintering stems present	P. crispus
3 Leaf margins entire or wavy; overwintering stems absent	4

4 Submersed leaves clasping; floating leaves absent	5
4 Submersed leaves not clasping, may be stalked; 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 heart-shaped; stem rusty or black-spotted; submersed leaves arced	P. amplifolius
6 Floating leaf blade wedge-shaped or rounded; stems without spots; submersed leaves not arced	7

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

8 Fruits plump, stalked; submersed leaf blade 7 – 9-veined	P. alpinus
8 Fruits compressed, not stalked; submersed leaf blade 3 – 19-veined	P. gramineus

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

10 Air spaces in leaf tissue present and prominent; submersed leaves with distinction between blade and stalk; leaves of two types, the floating ones long-stalked and wider than the submersed ones	P. epihydrus
10 Air spaces in leaf tissue absent or not prominent; blade and petiole not well-differentiated on submersed leaves; 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 tip tapered to pointed, leaves thin, 5 -7-nerved; inflorescence stalks at most 5 cm long	P. friesii
14 Leaf tip bristle-tipped; leaves firm, 3-nerved; inflorescence stalks 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 widest at the top; inflorescence stalks 1 – 3 per plant; leaf blade with less than 2 rows of air spaces along midrib	P. pusillus ssp. pusillus
16 Mature fruits widest at the middle; inflorescence stalks more than 3 per plant; leaf blade with 1 – 5 rows of air spaces along midrib	P. pusillus ssp. tenuissimus