Spatiotemporal distribution of epicormic shoots and their architecture in branches of Fraxinus pennsylvanica

Epicormic shoots in the branch systems of Fraxinuspennsylvanica var. subintegerrima (Vahl) Fern, (green ash) were more common on lower order shoots and arose periodically over a number of years, resulting in a greater number in older crown regions. Nevertheless, considerable variation existed among trees, ranging from 3 to 34 epicormic shoots per branch sample. Epicormic shoots were generally located near the distal end of parent shoots, suggesting their origin from persistent buds in these regions. The mean divergence angle of epicormic shoots was almost 10° greater than that of nonepicormic shoots. Mean length did not differ between epicormic and nonepicormic shoots, but the length of daughter terminal shoots extending epicormic shoots was considerably less than the length of those extending nonepicormic shoots. The number of lateral shoots produced by the two shoot types did not differ. The significance of epicormic shoot production to crown development and maintenance is discussed.