WHITE PINES OF WESTERN NORTH A>ERICA 225 



Western White Pine (-jk-.-.s ~:--.zi 2:la) 



Western white pine occurs naturally from southeastern British Columbi; 

 and extreme southwestern Alberta southward into northwestern Montana, 

 northeastern Washington, and northern Idaho to northeastern Oregon. 

 Further west it occurs from southwestern British Columbia southward 

 through western Washington and Oregon, northern California, and extreme 

 west -central Nevada to the southern Sierra Nevada Mountains of California 

 (Critchfield and Little, 1966; Map 6). 



In the northern part of its range western white pine has a broad 

 elevational spread--about 5,000 feet--but further south the spread is 

 restricted to about 1,500 feet (Wellner, 1962). The species generally 

 requires fairly moist sites, i.e., areas with 35 to 40 inches of precipi- 

 tation annually or, in drier areas, stream bottoms or north slopes. 

 Western white pine is a fire-perpetuated serai species in most areas. It 

 commonly occurs in mixed stands, but is also found in essentially pure 

 stands . 



Western white pine grows slowly during its first 10 to 15 years but 

 then maintains a rapid growth rate for several decades, reaching heights 

 Hp to 220 feet and diameters to 7 feet (Pomeroy and Dixon, 1966) . Young 

 seedlings are very sensitive to injury by frost heaving or drying winter 

 winds. If not protected by a covering of snow or adequate windbreaks. 

 nursery stock may be killed outright and transplants 10 to 15 years old 

 may be killed or severely defoliated. On excellent sites in northern 

 Idaho 120-year-old trees will average 175 feet in height and 22 inches 

 in diameter (Wellner, 1962, Figs. 9 and 10). Dominant and codominant 

 trees at age 80 in a well-stocked stand on an excellent site average 

 about 132 feet tall and 17 inches in diameter making up a volume of about 

 77 thousand board feet per acre (Haig, 1932) (Fig. 11). 



In the Cascade Mountains of Washington and Oregon, western white 

 pine is also an important stand component but usually occurs in relatively 

 small, scattered blocks rather than occurring over extensive areas as in 

 northern Idaho. Trees in the Sierra Nevada Mountains of California grow 

 at such high elevations that they are often deformed by wind and snow. 



Western white pine is highly susceptible to the white pine blister 

 rust disease (see Bingham 2 ) . 



Virtus montioola has been crossed successfully with 6 other species 

 of Subsection Strobi (Little and Righter, 1965; Wright, 1959) and putative 

 hybrids have been obtained from crosses with 3 species of* Subsection 

 C&mbrae (Bingham, Hoff , and Steinhoff , in press) . Hybrid combinations 

 involving ?. griffitkii 3 P. strobvs s Pinus peuoe Griseb., and Pinus 

 parvi flora Sieb. & Zucc. are being investigated at several stations 

 throughout the world. 



