Radiocarbon dating of a monumental dragon tree (Dracaena draco (L.) L.)

Abstract

Some arboreal monocotyledons, such as the dragon trees (Dracaena sp.), can develop impressive trunks (>5 m perimeter) through a lateral meristem, but their ages are difficult to determine. We report here a series of calibrated radiocarbon (C-14) dates obtained from a stem section of Dracaena draco (L.) L. subsp. draco growing on the island of Tenerife, Canary Islands, Spain. This radial section, about 40 cm long, was cut on October 18, 2023, from a large (similar to 60 cm diameter) branch that had fallen off the main stem of a privately owned dragon tree. In order to apply C-14 calibration, and given the lack of clearly defined growth layers, we collected 33 sequential samples at similar to 1-cm intervals along this radial section. A first attempt at wiggle-matching resulted in a calibrated dating of similar to 1787 CE for the innermost sample. Because we only knew the spatial distance, but not the time interval, between C-14 dates, we further applied calibration tools commonly used for sedimentary sequences. The Poisson-process deposition model in the software OxCal resulted in a calibrated age for the innermost sample of 1776-1798 CE (2 sigma). The classic and Bayesian age-depth deposition models available as R packages dated the innermost sample to, respectively, 1775-1862 and 1768-1813 CE. Because the branch was at a height of similar to 3 m from the ground, and its section did not reach the pith, our results suggest that this dragon tree was similar to 300 years old in 2023.