ASHS 2025 Conference

Ornamental plants are essential components of both rural and urban landscapes, with the horticultural industry generating $2.01 billion in bedding and garden plant sales in 2019. However, increasing drought stress, affecting 99.3% of Utah in 2023, highlights the need for water-efficient landscaping. Water-wise landscaping offers a promising solution by conserving water while maintaining visual appeal, making it increasingly popular in arid and semi-arid regions. This study was to investigate the effects of deficit irrigation frequency on the morphological and physiological of 13 landscape plant taxa: Caryopteris ×clandonensis ‘Blauer Splatz’ (Sapphire SurfTM bluebeard), Cercis canadensis (eastern redbud), Cercis occidentalis (western redbud), Cotoneaster ×suesicusn ‘OSUCOT2’ (Emerald BeautyTM cotoneaster), Hesperaloe parviflora ‘Straight Up Red’ (‘Straight Up Red’ Texas red yucca), Miscanthus sinensis ‘NCMS2B’ (bandwidth maiden grass), Penstemon barbatus ‘Novapenblu’ (Rock CandyTM blue penstemon), Penstemon pinifolius (pineleaf beardtongue), Penstemon strictus (rocky mountain beardtongue), 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 vitex). The experiment was conducted at the Utah Agricultural Experiment Station’s Greenville Research Farm in North Logan, UT, from 1 Jun to 31 Oct 2024. Eight plants per species were randomly assigned to one of three irrigation frequencies based on reference evapotranspiration (ETo): high (80% ETo), moderate (50% ETo), and low (20% ETo). Overall plant appearance was evaluated biweekly using a visual rating scale from 0 (dead) to 5 (excellent). Plant growth, stomatal conductance, and canopy temperature were recorded monthly. Net photosynthetic rate, transpiration rate, and vapor pressure deficit were measured in August and September. Results indicate species-specific responses to deficit irrigation. Some species, such as P. barbatus and P. strictus, exhibited improved visual quality, lower canopy temperatures, and higher photosynthetic rates under more frequent irrigation. In contrast, other species were not affected by reduced irrigation frequency.