Populus deltoides
 
Cottonwood

Leaf Bottom

Glenburn Regional Park
09-August-2007

Note that the key to the species in Budd's Flora is somewhat confusing.  It requires leaves not coarsely toothed, in order to distinguish P. deltoides from P. grandidentata.  It then requires leaf margins coarsely dentate in order to distinguish P. deltoides from P. tremuloides.  However, in the Canadian prairie provinces P. grandidentata is found only in the southeastern boreal forest, so if you are not in that region that species can be eliminated.

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Deltoides: Answers to key questions in Budd's Flora and Flora of Alberta leading to this species. 
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bark of trunk deeply furrowed; NOT [bark of trunk (well above base) smooth (FOA)

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bark of trunk usually grey; NOT [bark of trunk light green or whitish] (FOA)

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leaf blades broadly deltoid to cordate; NOT [leaf blades suborbicular] (FOA)

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leaves NOT coarsely toothed (BF)

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leaf margins coarsely dentate; NOT [leaf margins finely crenate] (BF)

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leaf blades coarsely toothed, often crenate; NOT [leaf blades crenulate or nearly entire] (FOA)

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leaf blades 5-10 cm long; NOT [leaf blades 2-6 cm long] (FOA)

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petioles strongly flattened laterally; NOT [petioles circular in cross-section, not flattened] (FOA)

 

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Populus: Answers to key questions in Budd's Flora and Flora of Alberta leading to this genus. 
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trees; NOT [mostly shrubs]

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winter buds covered by several scales; NOT [winter buds covered by a single scale]

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catkins soon drooping; NOT [catkins erect or divergent, rarely drooping]

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bracts below flowers mostly lacerate; NOT [bracts below flowers entire or merely toothed]

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flowers with a broad or cup-shaped disk; NOT [disk none]

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stamens usually more than 10; NOT [stamens 2-10, often 2]

 

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Salicaceae: Answers to key questions in Budd's Flora  leading to this family. 
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shrubs or trees; NOT [herbs]

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flowers with only one floral ring, with sepals but not petals

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male flowers, at least, in catkins or aments; NOT [flowers not in catkins or aments]

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seeds each with a tuft of hairs; NOT [seeds without a tuft of hairs]