Reaction of Selected Herbaceous Perennials to Low-input Cultural Practices and Severe Heat and Drought Conditions

The focus of this multi-year Earth-Kind^® research study was to investigate the reactions of 69 different species or cultivars of herbaceous perennials to low cultural inputs, disease and insect pest pressure, and severe heat and drought conditions.  A goal of the research was to determine what percentage of carefully selected, highly recommended herbaceous perennials would perform at a high level when grown using the Earth-Kind Environmental Soil Management approach of compost and mulch only. The location of the research was Myers Park and Event Center, McKinney, Texas.  During May of 2010 the plants were installed in alkaline, Houston Black Clay soils amended with 3 inches of fully finished, plant derived compost. A three-inch-thick layer of locally available wood mulch was applied to the soil surface and maintained at this thickness throughout the study.  These plants received no fertilizer, no pesticides of any kind, no removal of spent blooms, and no pruning other than the routine removal of winter-damaged tissue.  The perennials were evaluated throughout the growing season for landscape performance, nutrient deficiencies, disease susceptibility, insect injury, drought tolerance, plant size, and vigor.  Landscape performance, including heat and drought tolerance, was exceptional for 34 cultivars.  Many of the cultivars exceeded the mature height and width dimensions listed in reference sources.  During the second year of testing, the plants were subjected to the worst drought in this area in the past 75 years.  The plants received supplemental irrigation only one time, in mid August, during this very stressful 12-month period. This represents a 97.5% reduction in supplemental irrigation. Some cultivars, such as Anisacanthus quadrifidus, Eupatorium greggi, Malvaviscus arboreus, Wedelia hispida, and numerous species of Salvia showed extraordinary drought tolerance.  Incidence of diseases and insects throughout the two years of the study were minimal. Only four species of plants exhibited any nutrient deficiencies, with nitrogen deficiency being the most common. Results of this study identified multiple species and cultivars of herbaceous perennials suitable for growing in low-input landscapes consistent with the Earth-Kind management strategy