Betula occidentalis


River Birch

Emerson Bridge
Red Deer River, Alberta
12-August-2001

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.

 
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Occidentalis:  Answers to key questions in Budd's Flora and Flora of Alberta leading to this species.  
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usually found along streams; NOT usually found in forests, hills, or dry bogs

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

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bark of trunk NOT separable into thin layers

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

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

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leaves usually doubly serrate; NOT simply serrate or crenate

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leaves indistinctly reticulate; NOT distinctly reticulate

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wings usually broader than the nutlet; NOT narrower

 
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Betula: Answers to key questions in Budd's Flora and Flora of Alberta leading to this genus. 
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staminate flowers usually three in the axils of the catkin bracts; NOT solitary in the axils of the catkin bracts

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stamens 2; NOT 4

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

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

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

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

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

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male flowers, at least, in catkins or aments

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styles 2; NOT 3

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seeds WITHOUT tuft of hairs

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fruit NOT an acorn