COMPARISON OF SPRING FROST TOLERANCE AMONG DIFFERENT HIGHBUSH BLUEBERRY (VACCINIUM CORYMBOSUM L.) CULTIVARS
The spring of 2000 was warmer than most years in central Poland. By the end of April, most blueberry (Vaccinium corymbosum) cultivars began to bloom and some of them were in full bloom. Cultivars tested include Patriot, Darrow, Earliblue, Bluecrop, Berkeley, Blueray, Spartan, Lateblue and were at blossom stage 6.5, 5.9, 6.0, 5.0, 5.7, 5.0, 5.5, 3.5, respectively. On May 3rd, from 3 to 6 a.m. a heavy frost occurred. Temperature decreased to 6°C, and lasted for three hours. Most of the blueberry flowers were injured, especially the early-flower cultivars Patriot, Darrow, and Earliblue Flower injury was 84.69%, 82.98%, and 72.95%, respectively which was much higher than mid-season cultivars: Bluecrop, Berkeley, Blueray, and Spartan. The late-flowering cultivar Lateblue avoided the frost injury because of its late blossom, the injury to flowers was only 10.77%. Fruit set was 49.56%, 12.06%, 51.64%, 49.25%, 45.76%, 60.91%, 67.86%, 95.38% and percent berries produced for these eight cultivars were: and 41.59%, 10.64%, 21.31%, 35.82%, 37.29%, 54.55%, 44.05%, 92.31%, respectively. Three early-flowering cultivars Patriot, Darrow, and Earliblue showed differences to frost injury: Patriot had a higher number of injured flowers but high initial fruit set and high final set of berries produced, but most of the berries were quite small and had no seeds. Darrow showed a higher flower injury and low initial fruit set and final berry set. Earliblue had a higher flower injury but a medium initial fruit set rate and low final berry set with 41.27% berries dropped during the berry development. Symptoms of frost on flowers also showed on berries during their development. Some injured berries could develop and ripen, but most of them were small and had no seeds. This frost almost had no influence on initial fruit set and final berries set on the late-flowering cultivar Lateblue.
Lin, W. and Pliszka, K. (2003). COMPARISON OF SPRING FROST TOLERANCE AMONG DIFFERENT HIGHBUSH BLUEBERRY (VACCINIUM CORYMBOSUM L.) CULTIVARS. Acta Hortic. 626, 329-333
highbush blueberry, spring frost, injury, fruit set, Vaccinium ashei