Effect of winter chilling on Bartlett pear and Jonathan apple trees

Observations of the test trees in this study indicate that (presumably because of in-continuity of chilling) a varying portion of apple and pear buds may fail to open, even after a winter such as 1964–65 which provided 1,560 hours of chilling temperatures. Good chilling during both December and January is especially critical. Since winter-chilling is insufficient, or poorly distributed in the important pear-producing districts of the state more often than in the apple districts, the results emphasize the importance of heading back vigorous upright branches on young pear trees to insure near-to-normal foliation and branching. Except after the mildest winters, or with varieties having a high chilling requirement like Rome Beauty, such a pruning practice is seldom beneficial on apple trees, however.