Classic plant breeding has increased the beauty and utility of ornamental plants, but biotechnology can offer completely new traits for plants used in homes and gardens.  The creation of blue petal color in carnations and roses are examples where biotechnology has created novelty that conventional hybridization cannot match.  However, all innovations have benefits and risks, and future commercialization of transgenic ornamental plants raises complex questions about potential negative impacts to managed landscapes and natural ecosystems.  Predictive ecological risk assessment is a process that uses current knowledge to estimate future environmental harms or benefits arising from direct or indirect exposure to a genetically-modified (GM) plant, its genes, or gene products.  This article considers GM ornamental plants in the context of current ecological risk assessment principles, research results, and current regulatory frameworks.  The use of ecological risk assessment by government agencies to support decision-making is reviewed in the context of ornamental plants.  Government risk assessments have usually emphasized the potential for pollen-mediated gene flow, weediness in managed areas, invasion of natural areas, and direct harm to nontarget organisms.  Some of the major challenges for predictive risk assessment include characterizing gene flow over time and space, plant fitness in changing environments, and impacts to nontarget organisms, communities and ecosystems.  The lack of baseline information about the ecology and biodiversity of urban areas, gardens, and natural ecosystems limits the ability to predict potential hazards, identify exposure pathways, and design hypothesis-driven research.  The legacy of introduced ornamental plants as invasive species generates special concern about future invasions, especially for GM plants that exhibit increased stress tolerance or adaptability.  While ecological risk assessments are a valuable tool and have helped harmonize regulation of GM plants, they do not define the acceptable level of risk or uncertainty.  That responsibility belongs to regulators, stakeholders and citizens.