Carefully wash the sample collected with the core, taking care to prevent the shoots from
detaching from their insertion in the horizontal rhizome. Estimate the number of rhizome
segments (+ number of standing leaves) each shoot produced over its life span, thereby
obtaining an estimate of shoot age, in units of number of plastochrone intervals. The age of at
least 200 shoots, preferably > 500 shoots, must be determined to obtain reliable results. Plot
the frequency distribution of shoot age to identify the presence of peaks (cohorts), and then
determine the age difference (number of rhizome segments) in between them (Figure 8-5).
The age differences, as number of rhizome segments, in between peaks corresponds to an
estimate of the number of rhizome segments produced annually, from which the plastochrone
interval (365/number of rhizome segments produced annually) can be derived.