Low temperature survival of 'Redhaven' peach floral buds on selected rootstocks
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The relative cold tolerance of 'Redhaven' peach floral buds grafted onto various rootstocks was evaluated at selected dates from November 2011 to March 2013. Budwood was collected from trees in coordinated rootstock trials at New Franklin, MO and Clemson, SC for artificial freezing tests in late fall, mid-winter, and early spring. Samples were cooled 3 �C/h, thawed, and 'Redhaven' floral bud T50 values for each rootstock were calculated from the number of dead buds per test temperature. Although winter temperatures were unseasonably warm during this study, 'Redhaven' floral buds varied in cold tolerance among the rootstocks grown in Missouri in February 2012 and March 2013. In February 2012, 'Redhaven' floral buds on trees with KV010-127 and HBOK 32 rootstocks were the most cold tolerant, but in March 2013, those on Guardian rootstock were the hardiest. For South Carolina, 'Redhaven' floral buds on trees with Lovell and Viking rootstocks were the most hardy in January 2012, which was the only sampling date in which T50 values differed among rootstocks. When data were pooled from both locations, mean 'Redhaven' floral bud T50 values were always lower in Missouri than in South Carolina at similar collection periods. Also, buds from trees on Lovell, Guardian, Bright's Hybrid #5, and HBOK 32 rootstocks were hardier than those on Controller 5 and Mirobac rootstocks.