REMOVAL OF SECONDARY BURS INCREASES AVERAGE NUT WEIGHT FROM PRIMARY BURS OF ´ARMSTRONG´, ´ORRIN´ AND ´WILLAMETTE´ CHINESE CHESTNUTS

A study was conducted to determine the effect of secondary (2°) bur removal on primary (1°) nut weight of Chinese chestnut (Castanea mollissima) and to ascertain the effect of this treatment on subsequent vegetative and reproductive growth in the following growing season. The following four treatments were imposed on terminal shoots of chestnut trees that produced 1° burs: 1) 2° burs were removed; 2) 2° burs were not removed; 3) terminals with 2° catkins (but no 2° burs) were labeled; and 4) terminals without 2° catkins or 2° burs were labeled. On 3 Sept. 2003, the maximum number of 2° burs removed from individual shoots of ‘Armstrong’, ‘Orrin’ and ‘Willamette’ trees was 16, 28, and 14, respectively. The mean diameter of 2° burs of ‘Armstrong’, ‘Orrin’ and ‘Willamette’ at the time of removal was 30.5, 24.2, and 16.3 mm, respectively. At harvest 2003, ‘Willamette’ had the greatest total nut weight from 1° burs but there were no differences among treatments. However, when 2° burs were removed from shoots, nuts from 1° burs of all three cultivars averaged 1.5 g more than those harvested from shoots where 2° burs were not removed. In 2004, shoots that had 2° burs removed in 2003 tended to have more 1° burs set in June. Secondary burs were not produced in summer 2004 and 1° nut weights were similar among treatments at harvest.