Field pretreatment of crown suckers for propagating hybrid hazelnuts

Hybrid hazelnuts [Corylus americana (Walter) x C. avellana (L.)] are being developed for their ecological and economic value as a new crop for the Upper Midwest, but lack of economically viable propagation methods is a significant bottleneck to their wide scale adoption. Thus far, mound layering has been the primary propagation method, but layering cannot produce the numbers of plants needed for large-scale production. Rooting hardwood stem cuttings is a possible alternative. In a factorial experiment, we evaluated two pretreatments, blanching with sawdust and application of IBA, applied to rapidly growing first year collar suckers in the field five months ahead of collection for rooting. These treatments simulated mound layering, but without girdling. Sawdust by itself significantly increased both quantity and quality of subsequent rooting, but IBA pretreatment in combination with sawdust produced even better results. Stem cuttings were rooted in a growth chamber, set at 22 C (72 F) and 60% relative humidity, with PAR of 320 umol^.m² s¹ for 16 hours per day. The lack of heat stress in the growth chamber likely also contributed to relatively high rooting relative to the humidity tents used in previous trials.