Although invasive species are defined by U.S. law as species that cause environmental or economic harm, we have a limited understanding of each concept. In my thesis, I use both ecological and economic methods to explore the impacts of nonnative plants. In Chapter 1, I report the results of a two experiments in which I tested whether plant-derived compounds have an impact on larval amphibian performance, and whether this effect is predictable by plant native/non-native status. I find that tannins, saponins, and leachate from certain plant populations impact amphibian survival, rate of metamorphosis, and size-traits linked to adult fitness. In Chapter 2, I report my findings from a survey of 285 public and private land managers from across the United States. In total, managers spend at least $4.6 million on Phragmites australis (common reed) control. Over 90% of these organizations have applied herbicide in the past five years, treating a total of 83,000 wetland hectares with 28,000-20,000,000 L of herbicide product. Despite this high expenditure of resources and chemicals, organizations report that they rarely accomplish management objectives. In Chapter 3, I use conjoint analysis, a method of non-market valuation, to describe the impact of invasive plants in terms of management trade-offs rather than dollar value. It is my hope that a more synthetic understanding of invasive plant management will lead to more economically and ecologically sustainable land stewardship. ii