Amur maple (Acer ginnala) is a medium sized street tree grown for its durability in challenging environments. Unfortunately, it has escaped cultivation from prolific seed production and is banned in multiple regions. To breed for reduced fertility, a ploidy series was developed including 3x, 4x, and 5x genotypes. As part of the evaluation for fertility, phenology of field plants including the range from diploid to pentaploid were evaluated between 2020 and 2023. Reproductive traits included first flower, 50% flowering, full flower, seed set, seed abortion, and seed ripening. Vegetative traits included first leaf, full leaf, first fall color, full fall color, and leaf drop. There were no differences in phenology of any reproductive or vegetative traits relative to ploidy, and across all genotypes there was a high degree of consistency in timing of all observed traits. Confirming simultaneous flowering of all genotypes will provide confidence in future data collected on relative fertility of accessions to facilitate cultivar release. Additionally, this study confirmed that ploidy does not alter early or late season events that may expose plants to more damage from frost events during these periods.
