Influence of Chilling Hours on Flower Bud Growth and Rooting Ability of Blueberry Budsticks

Budsticks from 3 rabbiteye blueberry cultivars (‘Baldwin,’ ‘Brightwell,’ and ‘Tifblue’) and 2 highbush blueberry cultivars (TH-275 and ‘Georgiagem’) were subjected to 0 to 650 hrs at 4.4 °C (40°F) to determine the effects of accumulated chilling on terminal flower bud growth and rooting ability. The cultivar X chilling hours interaction was significant for both flower bud growth and rooting ability. The 2 highbush cultivars had wider flower buds than the 3 rabbiteye cultivars. ‘Baldwin’ and ‘Georgiagem’ produced the best overall root systems. Chilling requirements ranged from 350 to 550 hr for the rabbiteye cultivars and 350 to 450 hr for the highbush. Except for rooting score of clone TH-275, the functional relationships between flower bud width or rooting score and chilling hours were non-linear. In general, chilling hours enhanced the growth of terminal flower buds and increased the rooting ability.