Variability in Pecan Flowering

Abstract

Efficient pecan orchard design requires accurate information concerning flowering patterns of cultivars. Methods of evaluating pecan flowering vary widely in the literature, and may influence reported patterns. Critical aspects of pecan flowering are reviewed, especially, as they relate to monitoring bloom. Dichogamy patterns are reported for 13 pecan cultivars observed over four years at Shreveport, LA. Patterns of flowering varied between years, with dates of inner scale split, pollen shed, and stigma receptivity being related to seasonal growing degree day accumulations. Cultivars did not flower in identical sequence in all years, but did consistently exhibit either protogyny or protandry. Data from 12 cultivars collected at Brownwood, TX in 1992 are evaluated in relation to previous reports of flowering for those cultivars in the 1972 and 1974 seasons. Dichogamy data for three consecutive years from New Mexico are also evaluated for patterns due to season. At all locations, date of first bloom varied by year. Pollen shed and pistil receptivity for a cultivar varied in relation to bloom dates of other cultivars in different years. Two cultivars may have altered patterns of bloom overlap in different seasons. When designing orchard configurations, planners should rely on observations made over several seasons, and from trees as close as possible to the proposed orchard location. Rather than attempting to pick two cultivars that closely overlap bloom, or choosing a certain number of protandrous and protogynous cultivars, it may be preferable to select multiple cultivars to provide early, mid-, and late-season pollen, with the pistillate receptivity period of key cultivars in the orchard being heavily targeted.