<p>Phenology investigates the periodicity of biological events related to plant growth. There is limited phenological information on ferns, particularly under disturbance conditions such as forest edges and fire. This study aimed to identify phenological patterns and responses to environmental factors and post-accidental fire events, including leaf production and mortality, and the number of leaves of <i>Cyathea mexiae</i> Copel. at the edge of a semi-deciduous seasonal remnant of the Atlantic Forest in Brazil. Twenty-four plants were monitored for 22 months, with 10 of them affected by fire. We quantified and compared leaf number, production, and mortality, and evaluated their relationships with environmental factors (rainfall, temperature, and humidity), considering two groups: burned and unburned. Trunk height was measured and related to phenological events. Only one plant died post fire. Burned and unburned groups showed no significant differences in trunk height, leaf number, production, or mortality. Both groups exhibited discontinuous and irregular leaf production and mortality patterns. Both groups produced leaves immediately post fire, though with differences in peak timing. Burned plants displayed a rapid peak in leaf production (September), earlier than the peak in unburned plants (November). Only leaf mortality in unburned plants was positively correlated with rainfall and humidity. This study demonstrated a rapid recovery in leaf numbers following accidental fire for <i>C. mexiae</i>. The study revealed non-seasonal trends in the leaf production patterns of <i>C. mexiae</i>, with fire potentially inducing leaf mortality, reducing the sensitivity of this phenophase to environmental factors, and altering the timing of peak leaf production between the groups.</p>