PROMOTION OF CONE PRODUCTION ON FIELD-GROWN EASTERN WHITE-PINE GRAFTSBY GIBBERELLIN A(4 7) APPLICATION/

Field-grown 4- and 9-year-old grafts of eastern white pine (Pinus stro bus L.) were sprayed or injected with gibberellin A(4/7). Treatments i n May-June significantly increased pollen-cone production. Spraying pr oduced more pollen-cone clusters per tree. Injection increased the num ber of clusters per branch and the number of whorls per tree producing pollen cones. Injection, but not spraying, in May-June produced more seed cones. However, spraying in August-September did not promote eith er pollen-cone or seed-cone production. Injection in August-September decreased the number of pollen cones per cluster and inhibited seed-co ne production. Present results indicate that treatments for pollen- an d seed-cone production are best carried out in May and June during the period of rapid shoot elongation.