Earlier Forecasting of Douglas-Fir Cone Crop Using Male Buds

Earlier forecasting of Douglas-fir cone crops depends upon some indirect method of estimating female cone buds before they differentiate in late August. This study discusses correlation of female with male buds, recognizable early by position on the twigs while female buds are still indistinguishable from vegetative buds. In 1964, at Corvallis, Oregon, samples of 12 trees each at 200-, 1,500-, 2,900-, and 3,600-foot elevations revealed about the same total number of buds per sample in spring; but by September, abortion of male buds diminished these numbers almost linearly with increasing elevations. Ninety percent had developed at 200 feet, whereas 93 percent had aborted at 3,600 feet. Female bud counts at three of four elevations correlated fairly well with nonaborted male counts, but were uncorrelated with total bud counts sampled on lateral twigs. Twig samples collected at monthly intervals showed that abortion was mostly over by late July. This finding permits reasonably accurate estimates in late July of the September female bud numbers. In this study, most of the male cone crop variation, and presumably female cone crop, could be explained by differential abortion of buds. The so-called aborted buds in male positions were found to contain live meristems and could be forced into vegetative growth. The majority of male bud abortion occurred in July irrespective of elevation.