Increasing Chinese chestnut primary nut weight and bur production by hand removal of secondary burs

Abstract

Treatments were imposed on shoots of 'Orrin' and 'Willamette' Chinese chestnut (Castanea mollissima Bl.) trees to characterize vegetative characteristics of bearing branches and to determine the effect of secondary (2o) bur removal on primary (1o) nut weight and 1o bur production in the subsequent year. Treatments imposed in 2006 included hand removal of 2o burs on shoots bearing 1o and 2o burs (R), 2o burs not removed on shoots bearing 1o and 2o burs (N), and labeling of shoots bearing 1o burs only (PO). Treatments were imposed on shoots with equal numbers of 1o burs to ensure a similar crop load of 1o nuts. In 2006, R and N treatments had greater shoot diameters, lengths, and numbers of leaves than those of PO treatments. R treatments on 'Orrin' trees had greater 1o nut weight per shoot than the other two treatments. Results for 'Willamette' trees were generally similar to those of 'Orrin' trees. In 2007, R treatments on 'Orrin' produced a greater number of bearing shoots, which generally had more 1o burs per shoot than the other treatments. Following an April 2007 freeze, 'Willamette' trees produced few 1o burs but produced a saleable crop of 2o nuts, whereas 2o nuts produced in 2006 were unmarketable due to low nut weights.