Climate-Ready Landscape Plants: Garden Roses Trialed at Reduced Irrigation Frequency in Utah, USA

Increased urban and suburban populations in the arid western United States have resulted in more water demand; however, water availability in the region has become limited because of inadequate precipitation. Recent droughts have led to restrictions on irrigating landscape plants. Garden rose (Rosa ×hybrida) is commonly used as flowering plants in residential landscapes, but its drought tolerance has not been widely studied. The objective of this study was to determine the impact of reduced irrigation frequency on visual quality, plant growth, and physiology of five garden rose cultivars, including ChewPatout (Oso Easy® Urban Legend®), Meibenbino (Petite Knock Out®), MEIRIFTDAY (Oso Easy® Double Pink), Overedclimb (Cherry Frost™), and Radbeauty (Sitting Pretty™). Twenty-four plants of each rose cultivar were established in a trial plot at Utah Agricultural Experiment Station Greenville Research Farm (North Logan, UT, USA) in Summer 2021. Plants were randomly assigned to one of three deficit irrigation treatments for which irrigation frequencies were calculated using 80% reference evapotranspiration (ETO) (high), 50% ETO (medium), and 20% ETO (low). The total volumes of irrigation water applied to each plant were 345.6, 172.8, and 43.2 L for the high, medium, and low irrigation frequencies, respectively, during the deficit irrigation trial from 12 May to 30 Sep 2022. Root zones were wetted more frequently as irrigation frequency increased from low to high irrigation frequencies. Decreased irrigation frequency increased the number of visibly wilted and damaged leaves on all rose cultivars. However, only ‘Meibenbino’ and ‘MEIRIFTDAY’ exhibited a reduction in overall appearance under decreased irrigation frequency. The relative growth indices of both ‘Meibenbino’ and ‘MEIRIFTDAY’ decreased by 6%, whereas the dry weights of their leaves decreased by 37% and 36%, respectively, as irrigation decreased from high to low frequencies. Roses in this study appeared to decrease stomatal conductance up to 51% when irrigation decreased from high to low frequencies, or when air temperature increased. ‘Meibenbino’ and ‘MEIRIFTDAY’ exhibited unacceptable overall appearance, growth reduction, and higher leaf–air temperature differences, and they were less tolerant to reduced irrigation. Although the ‘Radbeauty’ maintained plant growth under the reduced irrigation frequency, the large leaf size led to a more visibly wilted appearance and the potential for heat stress, thus impairing visual quality. ‘ChewPatout’ and ‘Overedclimb’ were most tolerant to deficit irrigation at 20% ETO and maintained plant growth with acceptable visual quality and lower leaf temperatures when they received one irrigation during the growing season

Climate-ready Landscape Plants: Garden Roses Trialed at Reduced Irrigation Frequency in Utah, USA

Increased urban and suburban populations in the arid western United States have resulted in more water demand; however, water availability in the region has become limited because of inadequate precipitation. Recent droughts have led to restrictions on irrigating landscape plants. Garden rose (Rosa ×hybrida) is commonly used as flowering plants in residential landscapes, but its drought tolerance has not been widely studied. The objective of this study was to determine the impact of reduced irrigation frequency on visual quality, plant growth, and physiology of five garden rose cultivars, including ChewPatout (Oso Easy® Urban Legend®), Meibenbino (Petite Knock Out®), MEIRIFTDAY (Oso Easy® Double Pink), Overedclimb (Cherry Frost™), and Radbeauty (Sitting Pretty™). Twenty-four plants of each rose cultivar were established in a trial plot at Utah Agricultural Experiment Station Greenville Research Farm (North Logan, UT, USA) in Summer 2021. Plants were randomly assigned to one of three deficit irrigation treatments for which irrigation frequencies were calculated using 80% reference evapotranspiration (ETO) (high), 50% ETO (medium), and 20% ETO (low). The total volumes of irrigation water applied to each plant were 345.6, 172.8, and 43.2 L for the high, medium, and low irrigation frequencies, respectively, during the deficit irrigation trial from 12 May to 30 Sep 2022. Root zones were wetted more frequently as irrigation frequency increased from low to high irrigation frequencies. Decreased irrigation frequency increased the number of visibly wilted and damaged leaves on all rose cultivars. However, only ‘Meibenbino’ and ‘MEIRIFTDAY’ exhibited a reduction in overall appearance under decreased irrigation frequency. The relative growth indices of both ‘Meibenbino’ and ‘MEIRIFTDAY’ decreased by 6%, whereas the dry weights of their leaves decreased by 37% and 36%, respectively, as irrigation decreased from high to low frequencies. Roses in this study appeared to decrease stomatal conductance up to 51% when irrigation decreased from high to low frequencies, or when air temperature increased. ‘Meibenbino’ and ‘MEIRIFTDAY’ exhibited unacceptable overall appearance, growth reduction, and higher leaf–air temperature differences, and they were less tolerant to reduced irrigation. Although the ‘Radbeauty’ maintained plant growth under the reduced irrigation frequency, the large leaf size led to a more visibly wilted appearance and the potential for heat stress, thus impairing visual quality. ‘ChewPatout’ and ‘Overedclimb’ were most tolerant to deficit irrigation at 20% ETO and maintained plant growth with acceptable visual quality and lower leaf temperatures when they received one irrigation during the growing season

Residential Adoption of Best Landscape Management Practices: Effects of Outreach to Reduce Non-Point Source Pollution

Urban waterways degradation due to runoff from residential areas can be reduced by adopting best management practices (BMPs) for irrigation, fertilizer, and pesticide use. Although stormwater runoff from urban areas has been studied extensively, we focus on single-family residential land use specifically. Outreach to individual households may have a measurable impact since decisions are being made here. We surveyed households to evaluate the effectiveness of education and outreach campaigns on self-reported use of water and chemicals and evaluated whether self-reported behaviors were reflected in the quality and quantity of water draining from the study areas before and after outreach efforts. Our research was conducted in California, which has a Mediterranean climate with distinct wet and dry periods. Runoff from residential landscapes during the dry season enters waterways undiluted by rainwater, making this runoff particularly detrimental to receiving waters. No significant differences in behavior and BMP adoption from before and after the education and outreach campaign was found. These results are not atypical and may be explained by several factors including the population approach to the survey, lag times between outreach and measurable effects, and the need for a critical threshold of adoption to be met for effects to be measurable

Residential Adoption of Best Landscape Management Practices: Effects of Outreach to Reduce Non-Point Source Pollution

Urban waterways degradation due to runoff from residential areas can be reduced by adopting best management practices (BMPs) for irrigation, fertilizer, and pesticide use. Although stormwater runoff from urban areas has been studied extensively, we focus on single-family residential land use specifically. Outreach to individual households may have a measurable impact since decisions are being made here. We surveyed households to evaluate the effectiveness of education and outreach campaigns on self-reported use of water and chemicals and evaluated whether self-reported behaviors were reflected in the quality and quantity of water draining from the study areas before and after outreach efforts. Our research was conducted in California, which has a Mediterranean climate with distinct wet and dry periods. Runoff from residential landscapes during the dry season enters waterways undiluted by rainwater, making this runoff particularly detrimental to receiving waters. No significant differences in behavior and BMP adoption from before and after the education and outreach campaign was found. These results are not atypical and may be explained by several factors including the population approach to the survey, lag times between outreach and measurable effects, and the need for a critical threshold of adoption to be met for effects to be measurable

Role of Sediments in Insecticide Runoff from Urban Surfaces: Analysis and Modeling

Insecticides, such as pyrethroids, have frequently been detected in runoff from urban areas, and their offsite transport can cause aquatic toxicity in urban streams and estuaries. To better understand the wash-off process of pesticide residues in urban runoff, the association of pyrethroids with sediment in runoff from residential surfaces was investigated in two watersheds located in Northern California (Sacramento County). Rainfall, flow rate, and event mean concentrations/loads of sediments and pyrethroids, collected during seasonal monitoring campaigns from 2007 to 2014, were analyzed to identify relationships among stormwater quality and rainfall characteristics, primarily using Principal Component Analysis (PCA). Pyrethroid wash-off was strongly related to sediment wash-off whenever sediment loads exceeded 10 mg; this value was conveniently selected as a threshold between dissolved and particle-bound control of off-site pyrethroid transport. A new mechanistic model for predicting pyrethroid wash-off profiles from residential surfaces at basin-scale was implemented in the Storm Water Management Model (SWMM). The accuracy of the model predictions was estimated by evaluating the root mean square error (RMSE), Nash–Sutcliff efficiency (NSE), and Kling–Gupta efficiency (KGE) for each pyrethroid detected (RMSEtot = 0.13; NSEtot = 0.28; KGEtot = 0.56). The importance of particle-bound transport revealed in this work confirms previous field investigations at a smaller scale, and it should be a key consideration when developing policies to mitigate pesticide runoff from urban areas

Role of Sediments in Insecticide Runoff from Urban Surfaces: Analysis and Modeling.

Insecticides, such as pyrethroids, have frequently been detected in runoff from urban areas, and their offsite transport can cause aquatic toxicity in urban streams and estuaries. To better understand the wash-off process of pesticide residues in urban runoff, the association of pyrethroids with sediment in runoff from residential surfaces was investigated in two watersheds located in Northern California (Sacramento County). Rainfall, flow rate, and event mean concentrations/loads of sediments and pyrethroids, collected during seasonal monitoring campaigns from 2007 to 2014, were analyzed to identify relationships among stormwater quality and rainfall characteristics, primarily using Principal Component Analysis (PCA). Pyrethroid wash-off was strongly related to sediment wash-off whenever sediment loads exceeded 10 mg; this value was conveniently selected as a threshold between dissolved and particle-bound control of off-site pyrethroid transport. A new mechanistic model for predicting pyrethroid wash-off profiles from residential surfaces at basin-scale was implemented in the Storm Water Management Model (SWMM). The accuracy of the model predictions was estimated by evaluating the root mean square error (RMSE), Nash⁻Sutcliff efficiency (NSE), and Kling⁻Gupta efficiency (KGE) for each pyrethroid detected (RMSEtot = 0.13; NSEtot = 0.28; KGEtot = 0.56). The importance of particle-bound transport revealed in this work confirms previous field investigations at a smaller scale, and it should be a key consideration when developing policies to mitigate pesticide runoff from urban areas

UC ANR research and education influences landscape water conservation and public policy

UC has been heavily involved in research and extension efforts impacting landscape water conservation legislation for over 30 years. In 1981, UC implemented the California Irrigation Management Information System, a network of weather stations that provides data for local estimates of plant water needs. Those estimates led to UC being able to advise the California Legislature on policies for maximum applied water allowances for residential and large landscaping projects. The allowances have been reduced significantly with UC guidance, and UC has helped landscapers to meet the increasingly restrictive requirements. Best practices that reduce water losses have been developed in collaboration with equipment manufacturers and landscaping specialists, and explained to end users. In addition, UC has developed the WUCOLS database, which classifies over 3,500 plants by their water needs. UC's involvement in landscape water conservation continues on many fronts, developing science and contributing to policy

UC ANR research and education influences landscape water conservation and public policy

UC has been heavily involved in research and extension efforts impacting landscape water conservation legislation for over 30 years. In 1981, UC implemented the California Irrigation Management Information System, a network of weather stations that provides data for local estimates of plant water needs. Those estimates led to UC being able to advise the California Legislature on policies for maximum applied water allowances for residential and large landscaping projects. The allowances have been reduced significantly with UC guidance, and UC has helped landscapers to meet the increasingly restrictive requirements. Best practices that reduce water losses have been developed in collaboration with equipment manufacturers and landscaping specialists, and explained to end users. In addition, UC has developed the WUCOLS database, which classifies over 3,500 plants by their water needs. UC's involvement in landscape water conservation continues on many fronts, developing science and contributing to policy