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The oak (Quercus) species of eastern North America are declining in abundance, threatening the many socioecological benefits they provide. We discuss the mechanisms responsible for their loss, many of which are rooted in the prevailing view that oaks are drought tolerant. We then synthesize previously published data to comprehensively review the drought response strategies of eastern US oaks, concluding that whether or not eastern oaks are drought tolerant depends firmly on the metric of success. Although the anisohydric strategy of oaks sometimes confers a gas exchange and growth advantage, it exposes oaks to damaging hydraulic failure, such that oaks are just as or more likely to perish during drought than neighboring species. Consequently, drought frequency is not a strong predictor of historic patterns of oak abundance, although long-term climate and fire frequency are strongly correlated with declines in oak dominance. The oaks’ ability to survive drought may become increasingly difficult in a drier future.

The coordination of plant leaf water potential (Ψ_L) regulation and xylem vulnerability to embolism is fundamental for understanding the tradeoffs between carbon uptake and risk of hydraulic damage. There is a general consensus that trees with vulnerable xylem more conservatively regulate Ψ_Lthan plants with resistant xylem. We evaluated if this paradigm applied to three important eastern US temperate tree species,Quercus albaL.,Acer saccharumMarsh. andLiriodendron tulipiferaL., by synthesizing 1600 Ψ_Lobservations, 122 xylem embolism curves and xylem anatomical measurements across 10 forests spanning pronounced hydroclimatological gradients and ages. We found that, unexpectedly, the species with the most vulnerable xylem (Q. alba) regulated Ψ_Lless strictly than the other species. This relationship was found across all sites, such that coordination among traits was largely unaffected by climate and stand age.Quercusspecies are perceived to be among the most drought tolerant temperate US forest species; however, our results suggest their relatively loose Ψ_Lregulation in response to hydrologic stress occurs with a substantial hydraulic cost that may expose them to novel risks in a more drought‐prone future.