Warm springs compress budbreak, affecting floral freezing risk in red (Acer rubrum) and silver maple (A. saccharinum)

Red (Acer rubrum) and silver maple (Acer saccharinum) flower before leafing out in the early spring, making them vulnerable to post-budbreak freezing (false springs), a risk climate change exacerbates. They also show interannual variation in fruit production (masting), but it is unknown whether this pattern is related to freezing damage after budbreak. We observed budbreak phenology and measured cold hardiness of floral and vegetative buds of both maple species from dormancy to spring budbreak in 2024 and 2025. We also collected buds three times in 2025, incubated them in growth chambers up to 22°C, and quantified their deacclimation velocity. Finally, we used regional phenological data to assess whether local variation in fruit production might depend on false spring risk. We established the physiological context of spring budbreak in our study species: Silver maple floral buds open first and when very cold hardy, need minimal chilling, and lose cold hardiness rapidly; red maple vegetative buds open last and when least cold hardy, need considerable chilling, and lose cold hardiness slowly; and red maple floral buds and silver maple vegetative buds are intermediate. Though low fruit production was found to correlate with warm March temperatures followed by late March cold spells, we did not find direct, mechanistic evidence that local cold weather killed floral buds, decreasing fruit production. Differential physiology of maple buds interacts with climate to determine phenology. Both study species are at low risk of false spring damage, although it is unclear whether and how variable spring weather affects masting dynamics.