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

Populus angustifolia 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 furrowed on lower portion of truck, smooth above; branches ascending, orangey to greenish-brown; branchlets glabrous; winter buds reddish, resinous, glabrous

Leaves:

alternate, simple, petiole short and terete, blade 5 – 12 cm long, lanceolate to ovate, base cuneate to subcordate, apex acute to acuminate, dark green above, pale green below, margins finely crenate

Inflorescence:

catkins appearing with the leaves, pendulous, 3 – 8 cm long, rachis slightly pubescent or glabrous; pedicels to 1.5 mm long

Flowers:

actinomorphic; bracts membranous, lacerate or lobed, caducous; nectar-disc cup-shaped, 1 – 2 mm wide; in staminate flowers stamens 10 – 20, filaments free; in carpellate flowers ovary conic or ovoid, stigmas 2 – 4

Fruits:

capsule subsessile, 3 – 7 mm long, narrowly ovate, rugose; seeds comose

POPULUS KEY FOR SPECIES FOUND IN SASKATCHEWAN

1 Blades lanceolate to narrowly ovate, at least 1.5 times as long as wide	2
1 Blades ovate to deltoid, less than twice as long as wide	5

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

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

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

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

6 Blades of early leaves ovate, apex acute; winter buds very resinous and fragrant	P. balsamifera ssp. balsamifera
6 Blades of early leaves deltoid; apex acuminate; winter buds very or slightly resinous, not fragrant	7

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

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