Chilling and Bud Break in Silver Maple2

Abstract

Abstract Silver maple (Acer saccharinum L.) goes dormant in the autumn and is greatly delayed in bud break unless the buds are exposed to prolonged low temperature. Approximately 1000 hours below 4°C (39°F) under natural conditions (early March in southern Illinois) will bring about bud break 2 to 3 weeks after juvenile plants are put under favorable growing conditions. Chilling in a dark cold room at 4°C (39°F) separated from natural changes required a greater number of hours, approximately 2000, for a similar response. Bud break for subterminal buds was earlier than for terminal buds on insufficiently chilled stem segments or larger plantlets. Terminal buds broke first with longer chilling periods. Rooted cuttings from adult trees had a greater chilling requirement than juvenile plant material, either micropropagated plantlets or segments from shoots. No geographic or provenance variation in response to chilling was observed within 11 provenances ranging from Mississippi to central Ontario to New Hampshire to West Virginia. Silver maple was similar to sugar maple and basswood in its chilling requirement. It was unlike red maple which has a chilling requirement in some but not all parts of its range.