Pollination and cone morphology affect cone and seed production in lodgepole pine seed orchards

Abstract

We describe the phenology and mechanisms of pollen-cone and seed-cone development in lodgepole pine in the interior of British Columbia and the methods for monitoring cone phenology, pollination, seed production, and causes of seed and cone losses in seed orchards over the 15-month reproductive cycle. Pollination lasted about 2 weeks, between mid-May and mid-June. Pollen shedding and female receptivity showed homogamy, protandry, or protogyny depending on weather, site, and year. Morphological and developmental features explain why pollination as early as stage 3 was most successful and why self-pollination led to a seriously reduced production of filled seed. Early pollination increased the seed potential per cone and consequently the filled seed per cone. Cone drop occurred when less than 80% of ovules were pollinated per cone and was higher in trees from Prince George than those in the Okanagan Valley. Misting of trees and mechanical blowing of pollen in the orchards did not increase filled seed per cone. Clonal effect was the most important factor in all trials and has implications for orchard management.