Late spring freezes often result in significant flower bud kill in deciduous fruit trees. Some products have been marketed as frost protectant compounds which purportedly protect flower stigmas and ovaries from freezing injury and death. Two of these compounds, Frost Free and Frostgard, were tested at two locations in South Carolina over three years. Varieties `Junegold', `Loring', `Redhaven', and `Jefferson' were treated with Frost Free (FF) in years 1988-1990 and with Frostgard (FG) in 1990. Significant differences in fruit yield and vegetative growth occurred during this period, but no consistent trends were evident. In 1989, FF-treated `Redhaven' and `Jefferson' trees averaged 10.5 and 21.8 kg more fruit/tree than the controls. However, no lethal cold temperatures occurred during the bloom period. In 1990, FG-treated `Redhaven' trees averaged 8.0 kg more fruit/tree than the control trees. The fruit from FF-treated trees were lower in Brix, had less red color, and vegetative shoot growth was slightly greater than that of the FG and check trees. These data suggest that Frost Free may have plant growth regulator properties.
More than 400 genotypes of Prunus were evaluated for “in field” rooting and survival from fall-planted hardwood cuttings treated with 2000 ppm IBA. Cultivars of European and Japanese plums originating from species and interspecific hybrids of the section (sect.) Prunus had the highest survival. Cuttings from cultivars of sand cherry (sect. Microcerasus) and peach (sect. Euamygdalus) averaged 28% to 54% lower survival than European and Japanese plums. Few cultivars of almonds (sect. Euamygdalus), apricots (sect. Armeniaca), and American plums (sect. Prunocerasus) rooted from hardwood cuttings. Chemical name used: 1H-indole-3-butyric acid (IBA).