Thesis (M.S., Natural Resources) -- University of Idaho, 2016 | Ecological restoration is a critical component to sustaining healthy human interactions with nature. Progressive land managers are integrating new science and restoration techniques into their practices enabling them to achieve the highest level of repaired landscape success. However, native species across the Great Basin are vastly understudied. Building a network of information to help understand the complexities of this diverse system is the key to successful restoration work. The goal of this project was to develop useful physiological information for the desired restoration candidate species, Eriogonum umbellatum (Polygonaceae: Sulphur-flower buckwheat). One consideration for estimating the potential fitness of a species within an environment and to measure its resistance to climate change is through cold hardiness acclimation and loss assessment. We evaluated seasonal adjustments by calculating the lethal temperatures at which 50% of a plant’s cells are damaged due to decreased temperature, described as the LT50. Five geographically distinct sulphur-flower buckwheat populations, represented as M, J, B, C, and W, were investigated on a six-week cycle across a complete year. These five populations represented an elevation range of 855 to 1856 meters, five Omernik level III and IV ecoregions, and 5 provisional seed zones. Using adjusted index of injury (IOI) values, non-linear regressions were performed to fit 3-paramater logistic sigmoidal functions to calculate the LT50 values. Repeated measures analysis of variance was used to identify differences indicated by the collection date*population interaction. Statistical significance was found between two populations on four occasions (October 2013 W-J, p = 0.0025790, March 2014 C-B, p = 0.0488780, March 2014 W-B, p = 0.0466285, and April 2014 M-J, p = 0.0229043). Even though statistical significance was not found between the date*population interaction for the majority of the sample period, biological significance was very clear. Tukey’s honest significance (HSD) test (? = 0.05) was deployed to separate means and help describe differences between the sample dates within populations. When individual populations were evaluated across sample dates, significance was detected within all five. One of the five populations was evaluated at the natural wildland site and a transplant location, to evaluate local adaptation effects and plasticity. Statistical significance was detected between the two locations for the March data, while other collection dates were similar. Sulphur-flower buckwheat was found to have a LT50 range of -10oC - -58oC across the calendar year. In the species’ most vulnerable state, the average LT50 was -13.8oC. In the species’ most cold hardy state the average LT50 value was -56.4oC. Understanding Eriogonum umbellatum population variation of cold hardiness vulnerabilities and strengths is a useful screening tool to ensure the selection of populations adapted to conditions at the planting site.