Pruning practices differentially alter biomass allocation and leaf morphology of two southwest landscape shrubs

Four pruning treatments were differentially applied to two landscape shrubs, Nerium oleander 'Sister Agnus' (oleander) and Leucophyllum frutescens 'Green Cloud™' (Texas sage) for three consecutive years. The pruning treatments were sheared every six weeks, sheared every six months, renewal pruned yearly or not pruned (control). The partitioning of shoot mass into stems and leaves, leaf morphology and leaf chlorophyll concentration were evaluated during the third year of pruning treatments. After three years, standing shoot mass of all pruned oleanders ranged from 44 to 54% less than those that were not pruned. Texas sage that were sheared every six months or not pruned had about 45% more standing mass than those that were sheared every six weeks or renewal pruned yearly. For both taxa, standing mass density was highest for shrubs most frequently pruned and pruning practices resulted in removal of 40 to 95% of all shoot growth as green waste. All shrubs that were renewal pruned yearly had a greater portion of standing mass as foliage. All shrubs that were sheared every six weeks had the lowest canopy leaf dry mass and specific leaf mass. Leaf chlorophyll concentrations during the summer season were generally highest for oleander shrubs that were not pruned. In conclusion, for oleander shoot growth response was related to the type of pruning and pruning frequency. In contrast, for Texas sage pruning regardless of method or frequency stimulated growth.