Invasive plants represent a serious threat to biodiversity, landscapes, and human health, and have striking socioeconomic consequences. They spread rapidly, and eradication measures in later stages of invasion are problematic. To fight invasions successfully, repeatable and efficient remote sensing methods based on timely monitoring are needed. However, the data resolution, cost, availability, and detection accuracy can be limiting. The seasonal dynamics and spectral characteristics of target invasive species are important, and mapping strategy therefore must reflect the morphological and structural features of the plant, and choose optimal data spatial, spectral, and temporal resolution to find the balance between precision and economic feasibility. UAS with high flexibility and low costs represents an ideal mean to explore the effect of phenology on the detection process. Comparison to the VHR satellite imagery with lower spatial and temporal but higher spectral resolution enables the study of trade-offs between the three components of resolution that can partly compensate for each other. UAS imagery helps to make eradication efforts precise, fast, and efficient, and can serve as a basis for prediction, monitoring, and management prioritization.