Plants rely on rainfall and groundwater to stay alive, with the relative proportion of each varying according to different factors such as rainfall seasonality and rooting depth. In periods of drought, plants must increase their dependency on groundwater; however, not all groundwater is the same. Some groundwater systems are recharged by recent precipitation, while others continue to transmit water from storms that happened several decades or even centuries in the past. In a 2021 paper published in Environmental Research Letters, Zach Meyers and his colleagues sought to answer an important question: do plants nourished by old groundwater do better than those dependent on young groundwater? They hypothesized that the former would do better during periods of drought because the old groundwater source would be less affected by the current climatic conditions and, thus, would vary less and be more consistent. From 2011-2017 California experienced its worst 6-year drought on record, prov...