Phenology monitoring is being conducted by Rollinson, Duckett, and multiple volunteers in the spring, summer, and fall beginning in 2017. The dataset currently includes 73 oak trees in The Morton Arboretum Oak Collection. Monitoring is conducted once per week, and traits monitored include bud burst, leaves, leaf size, leaf color, leaf fall, flowers/flower buds, open flowers, pollen release, fruits, ripe fruits, and fruit/seed drop. Monitoring follows National Phenology Network (NPN) protocols. Trees were selected to include up to three individuals, randomly selected, from major North American and European species.