Land managers striving to protect native biodiversity from the onslaught of invasive species often face a daunting task. Most native habitats are invaded by a multitude of non-native species while managers have limited resources to devote to invasive species control and ecological restoration. Managers frequently lack data to prioritize species for control. Evaluating the ecological impacts of each species using a full suite of experimental protocols is impossible due to the high costs and technical expertise required. While regional lists of invasive species can be helpful in identifying species with high ecological impact (e.g., the California Invasive Plant Council’s Invasive Plant Inventory) these lists often cover a broad area and may not reflect local differences in establishment, spread, and impacts of each species. Further, even focusing on species identified as invasive often leaves managers with a list of twenty or more species to control which may still be an impossibly large task. Here we test a protocol that relies on simple field measurements (patch area, number of outliers, cover, richness) to differentiate between non-native species and provide a comparative evaluation of ecological impact of each species. This protocol is meant to be simple enough for use by volunteers or interns in the field and to provide initial data that may either be used directly in a management prioritization scheme or to generate hypotheses to be tested with manipulative field experiments. Our analysis of eight non-native species (Phalaris aquatica, Foeniculum vulgare, Centaurea melitensis, Euphorbia terracina, Carduus pycnocephalus, Ricinus communis, Nicotiana glauca, Conium maculatum) in the Santa Monica Mountains of southern California indicates that simple observational measurements can show differences in potential ecological impacts between species, all of which are listed as invasive by the California Invasive Plant Council.