ASHS 2025 Conference

Native edible berry plants create additional opportunities for native plant growers and nurseries due to their dense nutrient content. However, their growth and physiology under nursery conditions have not been widely studied. Controlled-release fertilizers (CRFs) are commonly used in nursery production, yet their optimal application rates for native edible berry plants remain understudied. While overfertilization can lead to excessive nitrogen (N) leaching, underfertilization can limit plant growth. The objectives of this research were to determine the effects, in a greenhouse, of increased CRF rates ranging from 0 to 0.96 g·L⁻¹ N on the development and physiology of three native edible berry species: Elaeagnus commutata (silverberry), Rhus trilobata (skunkbrush), and Shepherdia argentea (silver buffaloberry). For each species, thirty plants were randomly allocated to receive 15N–3.9P–10K CRF treatments at five different nitrogen concentrations: 0, 0.12, 0.24, 0.48, and 0.96 g·L⁻¹ N. These application rates corresponded to 0%, 25%, 50%, 100%, and 200% of the manufacturer's recommended dose. Throughout the 50-day experimental period, all plants received manual irrigation with tap water. Across all three species, higher CRF application rates led to increased leachate electrical conductivity (EC) and nitrate-nitrogen (NO₃-N) concentrations, as well as enhanced relative plant growth index, total leaf area, leaf dry weight, photosynthesis rate, and stomatal conductance. Lower CRF rates resulted in decreased chlorophyll content, photosystem II efficiency, and leaf nitrogen content in E. commutata and R. trilobata, though root-to-shoot ratios were higher at these lower rates. Physiological parameters such as photosynthesis and stomatal conductance showed no significant increases beyond the 0.12 g·L⁻¹ N CRF rate, while growth parameters remained statistically similar at CRF rates above 0.24 g·L⁻¹ N. This research demonstrates that CRF application rates below the manufacturer's recommendation were sufficient to maintain growth and physiology of the three native edible berry species. Under our experimental conditions, the optimal application rate was determined to be between 0.12 and 0.24 g·L⁻¹ N, which effectively sustained plant growth and physiological responses while minimizing NO₃-N concentrations in leachate. This reduction in fertilizer application could decrease production costs for native plant growers and nurseries, providing both environmental and economic benefits while expanding opportunities in the growing market for nutrient-dense native edible plants.