This study measured a statistically representative number of 2-month-old and 2-year-old eucalyptus trees using both leaf cuvettes and dynamic branch chambers. It demonstrated equivalent isoprene results between the two enclosure methods, yet contrasting emission magnitude and speciation among age groups. Current seedling- and adult-tree-mixed emission factor databases may thus misjudge ozone and secondary organic aerosol simulation, thus age-resolved data will improve air quality forecasts.