FALL SOWING AND DELAYED GERMINATION OF 
WESTERN WHITE PINE SEED 1 
By W. G. Wahlenberg 
Forest Examiner , Priest River Forest Experiment Station f Forest Service , United 
States Department of Agriculture 
Experiments to determine the best time to sow seed of western white pine 
(Pinus monticola) have been under way in the northern Rocky Mountain region 
since 1912, partly in northern Idaho at the Priest River Forest Experiment Sta¬ 
tion, but mainly at the Savenac nursery on the Lolo National Forest in western 
Montana. Climate and soil combine to make the problem essentially local, 
but although the findings may not apply directly elsewhere the observations may 
be found suggestive. 2 
In order to understand the problem it is necessary to know something about 
what is termed the “ hold-over characteristic” of western white pine seed. Like 
the other five-needled pines, this species has a strong tendency not to germinate 
all of its viable seed the first season after spring sowing. At Savenac nursery 
this delayed or second-season germination is often as high as 50 per cent, and has 
been anywhere from 4 to 91 per cent of the total number germinating from spring 
sowings. There are several theories regarding the cause of this habit. Chief 
among them are, first, the presence of an impermeable seed coat, and, second, the 
need of an after-ripening process in the embryo. 
DISADVANTAGES OF SPRING SOWING AND HOLD-OVER 
GERMINATION 
Table I is based on data secured from spring sowing during three different years 
and shows the proportion of hold-over germinations to have been high in every 
case. The figures give no reason to consider early spring sowing any better 
than late spring for western white pine; nor do seasonal variations in rainfall seem 
to be directly connected with the results obtained. Precipitation for the year 
1914 was average, being but 0.5 inches above the mean amount, while 1915 and 
1916 were both fairly moist with 2.27 and 3.59 inches, respectively, above the 
mean. Artificial sprinkling, of course, is employed to counteract the effect of 
too little rain in dry seasons. 
Table I .—Germination by seasons of spring-sown western white pine 
Average percentage of sown 
seed germinating 
Average 
percentage 
of total 
Time of sowing 
Number 
of 
plots 
Number 
of 
seeds 
First 
season. 
Second 
season 
Both 
seasons 
germination 
which 
occurred 
during 
second 
season 
May 1,1914. 
1 
4,000 
4,000 
6.0 
10.9 
16.9 
64.5 
May 15,1914. 
1 
5.1 
11.1 
16.2 
68.5 
June 1,1914_ 
1 
4,000 
7.3 
12.4 
19.7 
62.9 
May 5,1915. 
6 
5,000 
6,000 
28.8 
13.0 
41.8 
31.1 
May 27,1915. 
6 
13.4 
22.2 
35.6 
62.3 
May 5,1916. 
6 
6,000 
6.0 
36.0 
42.0 
85.7 
1 Received for publication May 21,1924—issued November, 1924. 
1 The early experimental work in this project was carried on by E. C. Rogers, assisted by P. O. Kitchin. 
A number of their manuscript reports have been drawn upon to indicate the previous work. 
Journal of Agricultural Research, 
Washington, D. C. 
(1127) 
Vol. XXVIII, No. 11 
June 14,1924 
Key No. F-14. 
