Species: Populus angustifolia James

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Populus angustifolia James

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TAXONOMY

Family:

Salicaceae

Genus:

Populus

Species Synonyms:

Populus balsamifera var. angustifolia (James) S. Wats.
Populus canadensis var. angustifolia (James) Wesmael
Populus fortissima A. Nels. & J.F. Macbr.
Populus salicifolia Raf.
Populus X sennii Boivin
Populus tweedyi Britt.

Common Names:

narrowleaf cottonwood

DISTRIBUTION

Canada:

southwestern Alberta – southwestern Saskatchewan

Saskatchewan:

southwestern Saskatchewan; Cypress Hills

Ecoregion:

Cypress Hills

HABITAT

Saskatchewan:

small creek valleys

Canada:

streambanks, plains, and foothills

RARITY STATUS

Provincial Status According
to Harms (2003):

Endangered

Nature Conservancy Status:

G5 S1

Saskatchewan Species at
Risk Status:

None

COSEWIC Status:

None

Narrowleaf cottonwood is endangered because it is extremely rare and regionally restricted in Saskatchewan. This species is almost always locally sparse. Immediate or probable threats have been identified.

SPECIES DESCRIPTION

Height:

to 15 m

Stems:

diameter at breast height (dbh) 20 – 50 cm; bark greenish to light brown, shallowly roughened on lower portion of truck, smooth above; branches ascending, orangey to greenish-brown; branchlets hairless; winter buds reddish, sticky, hairless

Leaves:

alternate, simple, leaf stalk short and round, blade 5 – 12 cm long, lance-shaped to oval, base wedge-shaped to shallowly heart-shaped, tip acute to long-tapered, dark green above, pale green below, margins finely round-toothed

Inflorescence:

catkins appearing with the leaves, drooping, 3 – 8 cm long, rachis slightly hairy or hairless; flower stalks to 1.5 mm long

Flowers:

regular; bracts membranous, torn or lobed, early deciduous; nectar-disc cup-shaped, 1 – 2 mm wide; in male flowers stamens 10 – 20, filaments free; in female flowers ovary conic or ovoid, stigmas 2 – 4

Fruits:

capsule nearly stalkless, 3 – 7 mm long, narrowly oval, wrinkled; seeds bearing tufts of long, white, silky hairs

POPULUS KEY FOR SPECIES FOUND IN SASKATCHEWAN

1 Blades lance-shaped to narrowly oval, at least 1.5 times as long as wide	2
1 Blades oval to triangular, less than twice as long as wide	5

2 Leaf blades saw-toothed in the middle of the leaf; stamens 25 – 40; blades green on both sides	P. x acuminata
2 Leaf blades saw-toothed along the whole margin; stamens 10 – 25; blades lighter on the underside	3

3 Leaf stalks less than 1 cm long, less than one-third the length of the blade	P. angustifolia
3 Leaf stalks greater than 1 cm long, more than one-third the length of the blade	4

4 Leaves pale green to white, but not strongly bluish-waxy beneath; base wedge-shaped; first-year twigs orangey	P. x brayshawii
4 Leaves white and strongly bluish-waxy beneath; base rounded; first-year twigs reddish	P. balsamifera ssp. balsamifera

5 Leaf stalks strongly flattened; stamens 6 – 12; bark on trunk mostly smooth, usually white	P. tremuloides
5 Leaf stalks round or nearly so for most of their length or flattened; stamens 15 – 80; bark on trunk roughened, usually grey	6

6 Blades of early leaves oval, tip short-tapered; winter buds very sticky and fragrant	P. balsamifera ssp. balsamifera
6 Blades of early leaves triangular; tip long-tapered; winter buds very or slightly sticky, not fragrant	7

7 Blades of early leaves dark green above, light green below; margin coarsely saw-toothed or round-toothed, largest teeth 1 – 2 mm; leaf stalks nearly round	P. x jackii
7 Blades of early leaves light green above and below; margin coarsely round-toothed or saw-toothed or square-toothed, largest teeth 2 – 6 mm; leaf stalks flattened at the junction with the blade	8

8 Flower stalks 1 – 6 mm long; leaf base with 2 prominent glands	P. deltoides ssp. monolifera
8 Flower stalks longer than 6 mm; leaf base with 3 – 5 prominent glands	P. deltoides ssp. deltoides