Dark septate endophytes (DSEs)—a type of root-dwelling fungus—may be key allies in helping plants survive climate change. These fungi boost drought and salinity tolerance by improving water absorption, reducing oxidative stress, and enhancing nutrient uptake even in harsh soils. One standout species, Rutstroemia calopus, helped cucumber plants thrive with 80% less fertilizer, thanks to its growth-boosting effects. DSEs could offer a low-input path toward sustainable agriculture, supporting crops in a warming, drying world.