| Summary: | 2012 Spring. Includes bibliographical references. In response to a severe regional drought that afflicted much of Colorado in 2002, Colorado State University initiated a study to determine the impacts of progressively decreasing irrigation treatments on some common shrub species. Irrigation treatments were based on the evapotranspiration of a short reference crop (ETo). In 2008, four shrub species were planted for trialing: Cornus sericea L. 'Isanti' (redosier dogwood), Hydrangea arborescens L. 'Annabelle' (smooth hydrangea), Physocarpus opulifolius (L.) Maxim. 'Monlo' (Diablo® ninebark) and, Salix pupurea L. 'Nana' (arctic blue willow). In addition to the shrubs, Poa pratensis L. (Kentucky bluegrass) was used as a control. After giving the shrubs and turf one growing season to establish, treatments were applied in 2009 and 2010. The study was comprised of a field component and a lysimeter component. The field component had four treatments based on ETo (0%, 25%, 50%, and 100%) and the lysimeter component had three treatments (25%, 50%, and 100%). All four species were planted in the field component and only the redosier dogwood and smooth hydrangea were planted in the lysimeter component due to space limitations. Data collection in both components included canopy height and width, visual ratings, predawn leaf water potentials, end of season leaf area, and end of season leaf fresh/dry weights. The field component also included soil moisture readings, osmolality, and infrared readings of the Kentucky bluegrass. The lysimeter component required daily weight measurements during dry down periods. As watering amounts increased for the field dogwoods, ninebarks, and willows various characteristics (overall stress, aesthetic appeal, size, osmolality) were also positively affected. However, all tested replicates of these three species in the 0% treatment appeared acceptable for landscape use, as well. The hydrangeas in the 100% treatment had the highest visual ratings. In addition, the water potentials were more ...
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