California buckeye enters drought dormancy in midsummer bloom

July 13, 2026Marin Hills

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has begun its midsummer dormancy across the inland hills, dropping leaves while still bearing open flowers and developing fruits. Observations from early July across a broad belt from the Presidio through Orinda show the same pattern: this native deciduous tree is shedding in response to heat and water stress, not the cold dormancy that characterizes temperate deciduous species elsewhere. It is a survival strategy finely tuned to the Mediterranean climate.

This synchronized phenology — leaf fall, flowering, and fruiting happening together — is no accident. The Ohlone people harvested the forming nuts in this exact window, leaching out the bitter toxins and rendering them edible. That knowledge, built on generations of observation of this annual rhythm, reflects an ecological understanding that is only now being formally documented in scientific phenology records. The timing was never arbitrary; it was precisely calibrated to the tree's own biology.

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