Betula occidentalis


River Birch

Male Catkin

Crooked Lake Provincial Park
23-May-2004

Note that the key to the Betulaceae genera in Budd's Flora states that the nutlets are mostly broadly winged in Betula, but are narrow winged or with leathery margins in Alnus.  However, the key to the Betula species in Flora of Alberta describes one group of Betula species as having wings narrower than the nutlet, and the other group as having wings usually broader than the nutlet.

 

Occidentalis:  Answers to key questions in Budd's Flora and Flora of Alberta leading to this species.  

usually found along streams; NOT usually found in forests, hills, or dry bogs

small tree or large shrub; NOT large tree; NOT low shrub

bark of trunk NOT separable into thin layers

bark reddish, grayish brown, or brown; NOT whitish or silvery gray

leaves mostly 2.5-5 cm long; NOT 4-8 cm long; NOT 1-2.5 cm long

leaves usually doubly serrate; NOT simply serrate or crenate

leaves indistinctly reticulate; NOT distinctly reticulate

wings usually broader than the nutlet; NOT narrower

 

Betula: Answers to key questions in Budd's Flora and Flora of Alberta leading to this genus. 

staminate flowers usually three in the axils of the catkin bracts; NOT solitary in the axils of the catkin bracts

stamens 2; NOT 4

pistillate catkins elongated; pistillate flowers NOT in a short, bud-like catkin; pistillate flowers NOT few

bracts of pistillate catkins thin, 3-lobed, deciduous; NOT becoming thick and woody, NOT persistent

fruit a winged nutlet in the axil of a catkin bract; NOT a nut enclosed in a leafy, hispid involucre

nutlets mostly broadly winged; NOT wingless, NOT narrow-winged, NOT with leathery margins

 

Betulaceae: Answers to key questions in Budd's Flora leading to this family.

shrubs or trees

male flowers, at least, in catkins or aments

styles 2; NOT 3

seeds WITHOUT tuft of hairs

fruit NOT an acorn