Chilling Affects Budbreak of Ginkgo biloba L.

Abstract The effects of chilling and heat on budbreak of Ginkgo biloba L. seedlings were evaluated in a study initiated on October 1, 1999, and terminated on April 8, 2002. Chilling was a determinate factor in foliar budbreak for G biloba. Thirteen levels of chilling were applied to trees in increments of 100 hours, with twelve replications per treatment. Once the chilling requirement had been satisfied, increased chilling led to a decreased heat unit requirement, resulting in accelerated foliar budbreak and higher budbreak percentage. Trees receiving the same treatment for three consecutive years required a minimum of 100 chill hours plus 936 greenhouse hours to initiate budbreak, and a minimum of 500 chill hours plus 1168 greenhouse hours to reach 50 percent budbreak. In years one and two, trees receiving less than 100 chill hours failed to break bud and eventually died. In year three, trees receiving less than 100 chill hours broke an average of 0.05 percent buds per tree, but no subsequent growth occu...