In a 40-year-old western white pine plantation developed as a seed production area, heavy thinning and application of fertilizer in the fall significantly increased strobilus production the following spring. Applying fertilizer increased seed weight and cone length significantly, but thinning did not. Insects severely damaged the cone crop in the thinned stand. This study indicates that abundant seed crops, relatively free from insect damage, may be produced without expensive thinning and area preparation operations.
Barnes, Burton V. 1969. Effects of thinning and fertilizing on production of western white pine seed. Res. Pap. INT-RP-58. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Research Station. 14 p.