How phenology interacts with frost tolerance in Southeastern Himalayan Rhododendron species.

This article investigates the relationship between frost resistance and phenology—specifically leaf-out and flowering timing—in 12 evergreen Rhododendron species across elevational gradients in the Southeastern Himalayas. The study finds that while new leaves generally maintain a positive safety margin against frost damage across elevations by adjusting leaf-out timing, flowers remain vulnerable to frost damage during early growing seasons, especially at higher elevations and in early-flowering species. Frost resistance shows a strong phylogenetic signal, with closely related species exhibiting similar tolerance levels regardless of elevation, indicating evolutionary constraints alongside acclimation. The findings suggest an evolutionary prioritization of leaf survival over flower survival, with phenological adjustments and phylogenetic factors jointly influencing species distribution limits in seasonally cold climates.