The determination of the age of tropical trees and palms is of significant importance for ecological studies and designing sustainable forest management plans. Radiocarbon is a powerful tool that can potentially help the determination of ages and growth rates of these plants. However, the application of 14 C analyses has one important problem for trees without annual rings and palms: the calibration of 14 C measurements with common programs such as CALIBomb or OxCal gives erroneous determinations for wood formed between AD 1954 and 1964. This problem is illustrated here using samples from a tropical tree ( Otoba gracilipes ) and a tropical palm ( Oenocarpus bataua ). This study shows how the use of two adjacent samples can help to unambiguously determine the real age of the samples and their mean growth rates. For comparison, long-term growth measurements for both species were used and it was determined that 14 C analyses provide accurate determination of growth rates for tropical trees and palms. Furthermore, the application of 14 C analyses in palms allows the determination of the rosette stage, rarely quantified in forest inventories and life-history studies.