Dec. 15, 1925 
Studies in Western Yellow Pine Nursery Practice 1111 
Germination is affected by the influence of shade upon tempera¬ 
ture and moisture content of the soil. Shade influences survival by 
reducing excessive water loss of the young plants in transpiration, 
by decreasing the surface temperature and evaporation from the soil, 
and by making^ conditions more favorable for the growth and spread 
of damping-off fungi. Shade affects the survival and growth of 
transplants indirectly through its effect upon the rate of germination, 
since the seed which germinates earliest produces the largest and 
most vigorous seedlings for transplanting. 
Practically all the evidence from these experiments strongly sup¬ 
ports the conclusion that western yellow pine spring-sown seed beds 
should not be shaded where artificial watering is possible, under the 
conditions in northern Idaho and western Montana. Duplicate ex¬ 
periments in two successive seasons, one of which was moist and 
favorable and the other was unusually hot and dry, uniformly show 
that the largest and most rapid germination, greatest survival, and 
best growth in the seed bed is obtained without shade, and that the 
unshaded seedlings make, on the whale, the best record in the trans¬ 
plant beds* There does not even seem to be any advantage in the 
temporary use of light shade during the hottest, and driest part of the 
season, if water is frequently applied. 
The optimum condition for the seedling of this species appears to 
be full light and direct exposure to the sun at all times. 
PROCEDURE 
I 
Two sets of experiments were included in this study, one in 1913 
and one in 1914. The 1914 series was intended to check the results 
obtained in 1913 under different seasonal conditions, and to compare 
early spring sowing with the late spring sowing. The two seasons 
represented a wide contrast, 1913 being cool and moist, and 1914 un¬ 
usually hot and dry. All plots were located in the Meadow nursery 
in connection with similar shading experiments with Douglas fir and 
western larch. 
The original plan for the 1913 experiments included only two de¬ 
grees of shade—one-quarter shade and no shade—since previous nurs¬ 
ery experience had indicated that one-half shade was probably too 
heavy for an intolerant species like yellow pine. The no-shade and 
one-quarter shade plots were sown June 6, the late sowing being due 
to the unusually late season that year and unavoidable delays in get¬ 
ting the new nursery ready for sowing. At the end of the season, 
however, it was thought worth while to make a comparison between 
these two plots and another plot sown June 6 in a near-by bed which 
had been given one-half shade. This plot differed essentially from 
the other plots only in area, position in the bed, and degree of shade. 
Source of seed, date and method of sowing, depth of cover, character 
of soil, and other details of treatment were the same for all three plots. 
One-half shade was included as a regular feature of the 1914 series, 
and three plots, one for each degree of shade, were sown May 6 in 
adjacent beds. Except for the degree of shade, all essential features 
of treatment were similar for the three plots. 
Seed collected and extracted at the experiment station in the fall 
of 1912 was used for both the 1913 and 1914 experiments. All seed 
was sown broadcast and covered with clean sifted sand to a depth of 
