Illustrated Canadian Forestry Magazine^ December, jgjo 



'^73 



The Poplar Trees of Canada 



{By B. R. Morton, B. Sc. F. Ottawa) 



Some twenly-tivc or more species of 

 poplar ( Popnlus ) are known and tliese 

 are widely distributed throughout the 

 northern portion of both the Eastern and 

 Western Hemispheres. Seven or eight 

 species are native to Canada, some of 

 which are known as aspens and cotton- 

 woods. 



The native species include the As])en 

 (P. trcmuloides') also called trembling 

 aspen and while ])o])lar; the Large- 

 Toothed -Aspen ( 1'. grandidentata ) ; the 

 Balsam poplar. ( P. balsamifera) some- 

 times called black poplar, balm poplar 

 and tacamahac and balm of (jilead ; the 

 Cottonwood (P. deltoides) or Eastern 

 Cottonwood; the lllack Cottonwood (P. 

 tricliocarpa). or balm cottonwood ; the 

 Lanceleaf Cottonwood (P. acuminata) ; 

 the Narrow leaf Cottonwood (P. angus- 

 tifolia) and the Balm of Gilead (P. can- 

 dicans ) which by some authorities is 

 considered a variety of the Balsam ])oi)- 

 lar rather than a distinct species. 



The .\si)en ( P. tremuloides) has per- 

 haps tile widest (hstribution of any of 

 our iialive i)oi)lars. It extends com- 

 pletely across Canada from Labrador 

 and the south end of I ludson Bay to the 

 north of the Mackenzie river and Alaska. 

 It is found on a large variety of soils but 

 makes its best growth on well-drained 

 loam. It occurs most frequently in pure 

 stands or mi.xed with the balsam \)OX)- 

 lar bluli's of the ()])en jirairie of tlu' West. 



. / Sliart-lired Tree. 



The .Aspen is not a large tree, averag- 

 ing; about 40 feet in heiglu and 8 to 10 

 inches in dianictcT. The growth is rapid 

 but not persistent. The tree is not long 

 lived since it is unich subject to certain 

 fungus diseases causing early decay. The 

 tree is sometimes used in prairie towns 

 and cities for shade tree purposes Init is 

 not as satisfactory for this purpose a.s 

 some of the other poplars as it rarely de- 

 velops into a well shaped tree. 



'i'he aspen is a prolilic seeder and its 

 downy seed is carried long distances b\- 

 the wind. hOr this reason it is often the 



hrst tree to restock a burned area in the 

 northern woods. 



It can be readily distinguished from 

 the other native poplars by the shape of 

 its leaves which are almost circular in 

 outline and from one and a half to two 

 and a half inches long. The margin is 

 linely toothed, whereas the Large-Tooth- 

 ed .Aspen, as the name indicates, has its 

 leaf margin very coarsely notched. The 

 leaf stem of the aspen is very much flat- 

 tened in cross-section and therefore lack- 

 ing stififness. The slightest movement 

 of the air sets its leaves in motion. It 

 derives one of its names, trembling aspen, 

 from this fact. 



The Balsam Poplar. 



Tile Balsam poplar (P. balsamifera) 

 has practically the same range in Canada 

 as the Aspen and is frequently found in 

 mixed stands with that species. It at- 

 tains a greater size than does the aspen 

 l)eing a medium sized tree with a height 

 of 50 to 60 feet and a diameter of 1 to 2 

 feet. Contrary to what might be ex- 

 pected, the balsam poplar does not reach 

 its best development as a forest tree in 

 the more temperate parts of its range. 

 Its best development occurs in the north- 

 ern part of the ])rairie provinces, par- 

 ticularly in the Peace River country of 

 Alberta, idiis is perhaps due to the fact 

 that in that region it is occupying better 

 soils with less competition from other 

 species than it could further east and 

 south. 



The oval or egg-shaped leaves which 

 are from 3 to 5 inches long readily dis- 

 tinguish the balsam jioi^lar from either 

 the aspen or Large-lootheil Aspen. The 

 leaf stem is round on cross-section or 

 only the lower half is llattened. The win- 

 ter buds ;ire large and ctvUed with a 

 sticky, fragrant gum. 



The I.arge-toothed aspen ( W gr.indi- 

 dentala ) is contined largely to l^astern 

 ('anada. being found scattercil from 

 Xova Scotia and New Brunswick 

 throughout Ouebec and ( MUario south of 

 the height of land, dividing the waters of 

 the ( Ireat Lakes and lludson Bay ex- 

 tendinu iiUo southeastern Manitoba. 



