Utah has experienced significant drought conditions, with 99.3% of the land under drought stress from the previous year to the present. In response to this challenge, deficit irrigation landscapes are gaining popularity in arid regions. This study aimed to investigate the overall appearance, plant growth, and physiological response of ten ornamental plants to deficit irrigation. The selected species include Caryopteris ×clandonensis ‘Blauer Splatz’ (Sapphire SurfTM bluebeard), Cercis canadensis (eastern redbud), Cercis occidentalis (western redbud), Cotoneaster ×suesicus ‘OSUCOT2’ (Emerald BeautyTM cotoneaster), Hesperaloe parviflora ‘Straight Up Red’ (‘Straight Up Red’ texas red yucca), Miscanthus sinensis ‘NCMS2B’ (bandwidth maiden grass), Physocarpus opulifolius ‘Diabolo’ (Diabolo® ninebark), Physocarpus opulifolius ‘Little Devil’ (Little DevilTM ninebark), Rosa ×hybrida ‘Meifranjin’ (Blushing Drift® rose), and Vitex agnus-castus ×rotundifolia ‘Helen Froehlich’ (Summertime BluesTM chaste tree). Eight plants per species were randomly assigned to one of three deficit irrigation frequencies, calculated based on 80% reference evapotranspiration (ETo) (high), 50% ETo (medium), and 20% ETo (low) at the Utah Agriculture Experiment Station’s Greenville Research Farm, North Logan, UT, USA. The overall appearance was evaluated biweekly, spanning from 30 Jun to 31 Oct 2023. Plant growth and stomatal conductance were recorded monthly during the growing season. The growth of plants was not significantly affected by reduced irrigation frequency. However, the impact of deficit irrigation on aesthetic performance and stomatal conductance was notable, particularly during August and September. The results highlight variability in plant performance across species, with Caryopteris ×clandonensis and Cotoneaster ×suesicus showing consistent performance across irrigation levels. However, Cercis canadensis and Physocarpus opulifolius ‘Diabolo’ exhibited a more pronounced difference under varying irrigation levels. Funding Source USDA Agricultural Marketing Service Specialty Crop Multi-State Program, USDA NIFA Hatch project UTA01666, 2022 Extension Water Initiative Grants Program, Utah State University’s Center for Water-Efficient Landscaping, and the Utah Agricultural Experiment Station
