Response of 'Desirable' and 'Kiowa' Pecan to a Late-spring Freeze

This study was established to assess the effects of a severe late spring freeze on flowering, shoot growth, leaf nutrient status, and the retention of fruit developing from secondary buds of pecan [ Carya illinoinensis (Wangenh.) K.Koch]. Freeze damage appears to have a significant influence on pecan physiology and fruit retention. ‘Desirable’ produced a crop of pistillate flowers from secondary buds after the freeze; however, many of these flowers were abnormal in appearance. Freeze-damaged ‘Desirable’ trees exhibited shorter shoots, reduced flower and fruit retention, a lower chlorophyll index, and decreased leaf nitrogen concentration compared with nondamaged trees. Leaf zinc concentration was higher in freeze-injured ‘Desirable’ trees than in nondamaged trees. Freeze-damaged ‘Kiowa’ trees had longer shoots and failed to produce a crop of pistillate flowers from secondary buds on most shoots. Freeze damage led to the appearance of mouse-ear leaf symptoms and reduced leaf chlorophyll index, leaf nitrogen, and leaf magnesium concentrations in ‘Kiowa’. Leaf phosphorous and leaf potassium concentrations were higher in freeze-injured ‘Kiowa’ trees than in nondamaged trees. These observations provide insight into the potential response of bearing orchard trees injured by a late spring freeze.