218 



R. J. STETNHOFF 



Figure 3. Typical form of Pinus albicaulis in the Rocky- 

 Mountains in southwestein Montana (U.S. Forest Service photo). 



conditions, some individuals develop to a size and shape suitahle for 

 timber production (Fig. 4). Day (1967) reported a whitebark pine 107 feet 

 tall and 31 inches in diameter in the Crowsnest Forest in southwestern 

 Alberta. He also reported stands containing trees over 90 feet tall and 

 up to 36 inches D.B.H. in two areas of British Columbia. A stand of white- 

 bark pine growing in the Kaniksu National Forest in northern Idaho also 

 contained many large trees, most of which have been cut for timber. 



Planting of whitebark pine has been limited to special purposes such 

 as in arboreta. The finding of occasional large, timber-type trees indi- 

 cates that selection for desirable types is possible, although the species 

 is extremely susceptible to white pine blister rust disease (Bingham*) . 



Attempts have been made to cross P. albicaulis with most species of 

 subsections Cembrae and Strobi. Crosses with Pinus cembra L., Pinus 

 -pumila Regel, Pinus sibirica Du Tour, P. flexilis , and P. montioola have 

 yielded seed or seedlings but the putative hybrids are not yet large 

 enough for verification (C. Heimburger, personal oommuni cation 3 P. cembra 

 and P. sibirica; Institute of Forest Genetics, Placerville, Calif., 

 unpublished data, P. cembra, P. pumila, P. flexilis; Bingham, Hoff, and 

 Steinhoff , in press 3 P. monticola) . 



SUBSECTION STROBI 



Limber Pine (P. flexilis) 



Limber pine is another widely distributed white pine. It is found 

 throughout the Rocky Mountain chain from southern Alberta and British 

 Columbia to southern Colorado and north-central New Mexico. It is also 

 found in the mountains of south-central and southeastern Idaho and in 

 Nevada and Utah with a possible extension to north-central Arizona. In 

 California it occurs in the Sierra Nevada Mountains in the east-central 



