Following B sprays, fruit set increase in ‘Barcelona’ hazelnut was accompanied by a decrease in dry‐matter accumulation for the entire fruiting twig. In unsprayed controls prior to 5 June, leaves constituted 80% of the total dry weight of a fruiting twig. Later in the season (5 Aug.) the percent dry weight was maximum in the nut tissue (66%), followed by leaves (17%), and then husks (13%). Leaves contained 87% of the total B in a fruiting twig early in the season, indicating that the leaf was a major sink for B at that time. Of the net B increases over a 2 months period, 24% was in the leaves, 38% in the nuts, and 37% in the husks. By 5 Aug., compared to other tissues, stem dry matter (3%) and B content (32) was negligible; hence, the stem was of little importance in overall partitioning. Boron sprays did not alter B partitioning in the fruiting twigs.