Knowledge of how species differ in their flammability characteristics is needed to develop more reliable lists of plants recommended for landscaping homes in the wildland?urban interface (WUI). As indicated by conflicting advice in such lists, such characterization is not without difficulties and disagreements. The flammability of vegetation is often described as having four components (ignitability, combustibility, sustainability and consumability). No standards or generally recognized test procedures exist for evaluating these components in plants. Some measurements of flammability include times for ignition, rate of flame spread, flame height and heat release rate. Often, the fire behavior characteristics of a plant are derived from its physical and chemical characteristics. Thermogravimetric analysis and other thermal analysis of ground samples have long been used to characterize the thermal degradation of vegetation. More recently, researchers have used the oxygen consumption methodology to measure the heat released due to combustion of the vegetation. Although oxygen consumption calorimetry is an improvement in characterizing plant flammability, translation of laboratory results to field conditions can be problematic and tests can be expensive.