Populus deltoides
Cottonwood
Petiole Cross Section
Glenburn Regional Park
09-August-2007
Note how the petiole is flattened.
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.
 | Deltoides: Answers to key questions in
Budd's Flora and Flora of Alberta leading to this species.
 |
bark of trunk deeply furrowed; NOT [bark
of trunk (well above base) smooth (FOA) |
|
bark of trunk usually grey; NOT [bark of
trunk light green or whitish] (FOA) |
|
leaf blades broadly deltoid to cordate;
NOT [leaf blades suborbicular] (FOA) |
|
leaves NOT coarsely toothed (BF) |
|
leaf margins coarsely dentate; NOT [leaf
margins finely crenate] (BF) |
|
leaf blades coarsely toothed, often
crenate; NOT [leaf blades crenulate or nearly entire] (FOA) |
|
leaf blades 5-10 cm long; NOT [leaf
blades 2-6 cm long] (FOA) |
|
petioles strongly flattened laterally;
NOT [petioles circular in cross-section, not flattened] (FOA)
|
|
| Populus: Answers to key questions in
Budd's Flora and Flora of Alberta leading to this genus.
|
trees; NOT [mostly shrubs] |
|
winter buds covered by several scales;
NOT [winter buds covered by a single scale] |
|
catkins soon drooping; NOT [catkins erect
or divergent, rarely drooping] |
|
bracts below flowers mostly lacerate; NOT
[bracts below flowers entire or merely toothed] |
|
flowers with a broad or cup-shaped disk;
NOT [disk none] |
|
stamens usually more than 10; NOT
[stamens 2-10, often 2] |
|
| Salicaceae: Answers to key questions in
Budd's Flora leading to this family.
|
shrubs or trees; NOT [herbs] |
|
flowers with only one floral ring, with
sepals but not petals |
|
male flowers, at least, in catkins or
aments; NOT [flowers not in catkins or aments] |
|
seeds each with a tuft of hairs; NOT
[seeds without a tuft of hairs] |
|