In front of the United States Geological Survey (USGS) national headquarters building in Reston, Va., two genetically identical lilac bushes are rooted in the earth. To casual observers, they are fragrant adornments to the landscaped property. But to ecologist Jake Weltzin and geographer John Jones—USGS scientists who study plant and animal life-cycle events—they are “Li” and “Lac,” two small but important pieces of a developing climate change indicator system.