Evaluation of limited quality water on landscape ornamentals
Stoker, V. J Halbrooks
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The quality and quantity of irrigation water is a growing concern for urban and rural areas. The level of salinity in the natural water supply is on the rise due to natural weathering of minerals (Richards, 1954). Landscape plants that tolerate poor water quality could be beneficial for homeowners and growers. The objective of this study was to identify heat and drought tolerant landscape ornamentals that are also useful in areas with elevated salinity levels in the water supply. Treatments included a control and three salinity levels ranging from 1.56 to 6.25 dS/m. Many of the annuals and herbaceous perennials selected for inclusion in this study were Texas Superstar's™. Species chosen for this study Included Coleus X hybrida 'Plum Parfait' (Plum Parfait SuperSun Coleus), Cuphea hyssopifolia (Mexican Heather), Lantana x hybrida 'New Gold' ™ (New Gold ™ Lantana), Mattiholia incanna (Stock plant), Melampodium leucanthum (Blackfoot Daisy), Oenothera missouriensis (Missouri Primrose), Portulaca oleraceae 'Yubi™ (Large-Flowered Purslane), Salvia leucantha (Mexican Bush Sage), Scaveola aemula 'New Wonder™ (New Wonder™ Fan flower), and Verbena bipinnatifida (Prairie Verbena). The irrigation treatments were applied to the 10 species to achieve a minimum 30% leaching fraction each day. Weekly leachates were tested for EC and pH levels. This study took place in the container holding area outside of the Texas Tech University greenhouse in Lubbock, TX, and was repeated four times. Experiment 1 (studies 1 and 2), conducted in summer 2001, ran for a 13 week period, whereas experiment 2 (studies 3 and 4), conducted in 2002, ran for a six-week period. Final EC and pH were measured on the leachate. Final visual ratings were taken at termination of the study and days of survival were recorded along with the dry weights of the roots and shoot. Portulaca oleraceae was determined to be the most salt tolerant (EC 6.25) of the species studied, followed by Lantana x hybrida 'New Gold™ being moderately salt tolerant (EC 3.12). Further research to identify additional herbaceous annuals and perennials for salinity tolerance, and the level of salinity tolerated for desirable production, is recommended.