Irrigation Effects on Growth, Stress, Visual Quality, and Evapotranspiration of Ornamental Grasses

Information available about standard watering procedures of ornamental grasses is fairly nonexistent, and often not research based.  Finding exact water requirements of specific ornamental grass species is extremely valuable for large scale water savings.  It is important to determine precise irrigation needs of ornamental grass species, and test the limits to which the grasses can survive around those needs.  This research has the potential to represent a large range of ornamental grass species; serving as a platform for future studies on the subject.  The results will be an understanding of these grasses both in terms of physiological stress and ornamental aesthetics. Three genera of ornamental grasses were evaluated; Panicum virgatum ‘Rotstrahlbusch’ (Rotstrahlbusch Switchgrass), Schizachyrium scoparium ‘Blaze’ (Blaze Little Bluestem), and Calamgrostis brachytricha (Korean Feather Reed Grass).  These three genera were chosen to represent a diverse group of popular ornamental grass species.  All three genera were subject to irrigation amounts of 0%, 25%, 50%, and 100% relative to bluegrass evapotranspiration.  Five replications in each treatment were subject to these irrigation levels for the 2013 and 2014 growing seasons. Results showed all three species in the 25%, 50%, and 100% treatments were considered acceptable for landscape purposes.  The 25% treatment contained plants which had greater height, width, and circumference.  The 25% treatment resulted in grasses with the highest ornamental quality and landscape impact ratings, both measurements of aesthetic quality.  Physiologically, the 25% treatment grasses were in the lowest bracket of plant stress. A second research project was initiated in 2014, evaluating one species (Blaze Little Bluestem) which was subject to irrigation amounts of 25%, 50%, and 100% relative to bluegrass evapotranspiration.  Initial results indicated all plants in the study were acceptable for landscape purposes.  Grasses in the 25% treatment used 50% of the water, but were about 60% more stressed than the 100% treatment.  Grasses in the 50% treatment used 75% of the water, but were about 30% more stressed than the 100% treatment.  Coupling these studies together, initial results indicated that ornamental grasses which receive less water will use less water and can still result in healthy, beautiful plants and large scale water savings.