Relationships between shoot growth and rooting of cuttings in three contrasting species of ornamental shrub

Abstract

SummaryApical cuttings of the difficult-to-root Syringa vulgaris ‘Madame Lemoine’ rooted well only during a brief period of rapid shoot growth in early summer, and even then only when the stockplants had been severely pruned in the previous late winter. Rooting was poor early in the period of shoot growth and, after reaching a peak in early June, declined as shoot growth stopped. The relatively difficult-to-root Cotinus coggygria ‘Royal Purple’ behaved somewhat similarly to Syringa, with rooting being confined to the period of active shoot growth, which was longer than for Syringa, and with a smaller benefit from severe stockplant pruning. Forsythia x intermedia ‘Lynwood’ rooted well throughout the summer regardless of shoot growth rate and earlier pruning severity. In Syringa, the opportunity to enhance rooting, especially in cuttings from the less severely pruned source, by growing shoots temporarily in the dark, was limited to the period of active shoot growth. Producing a late flush of rapidly growing...