Studies were conducted to characterize bur and nut development on shoots of young chestnut (Castanea sp.) trees over a two year period and to determine the effect of secondary (2°) bur removal on subsequent bur and nut production. Terminal shoots of 'Peach' trees with primary (1°) and 2° burs (PS) grew longer and had greater stem diameter than those shoots with 1° burs only (PO), 2° burs only (SO), or with no burs (VO). PS shoots of ‘Peach’ had greater 1° nut weight per shoot than the other types of shoots in 2006. PS shoots also produced 2° nuts with as much or more weight per shoot than SO shoots. For ‘Peach’ trees, 2005 fruiting or vegetative shoots were most likely to develop a VO shoot in 2006. PS shoots of ‘Willamette’ trees typically produced more 1° nut weight per shoot than the other types of shoots. However, 2° nut weights per shoot were similar for PS and PO shoots on ‘Willamette’ trees. The odds of 2005 fruiting or vegetative ‘Willamette’ shoots developing into PO shoots the following year were ≥ 50%. When 2° burs were removed from shoots of ‘Orrin’ trees in late July (R treatment), 1° nut weight per shoot at harvest and the number of 1° bur-bearing shoots in the following year were greater than that on shoots where 2° burs were not removed (N treatment). Thus, 1° nut weights were enhanced by 2° bur removal, as well as subsequent 1° bur production. For ‘Willamette’ trees, R-treated trees also had relatively more 1° nut weight per shoot than PS-treated shoots at harvest in the year the treatment was imposed, but most 1° flowers were killed by an early April freeze event the following year. In spite of this loss, a marketable crop of 2° nuts was produced.
Warmund, Michele; Enderton, Darin J.; Van Sambeek, J.W. 2010. Bur and nut production on three chestnut cultivars. Journal of the American Pomological Society. 64(2): p 110-119.