The impact of pyrolysis gas composition and the underlying reaction kinetics on the burning characteristics of a leaf was computationally investigated. The computational configuration resembled a previous experimental setup where vertically oriented manzanita (Arctostaphylos glandulosa) leaves were burned. Different compositions and reaction kinetics for the pyrolysis gas released during the leaf thermal decomposition were examined. The most detailed composition included CH4, CO, CO2, and H2, which was suggested by the previous experimental study of pyrolysis products of different plant species. The least involved compositions only included either CH4 or CO. In all considered compositions, in addition to pyrolysis gas, the release of the heavy gas, i.e. tar, was accounted for. Tar breakdown was represented by a single-step reaction with the light gases above and soot as the products where the stoichiometric coefficients were determined by an optimization technique for consistency with the measurements for the tar molecule. The burning simulation results agreed best with the previous experimental data when a mixture of CH4, CO, CO2 was used. The least agreement was noted when pyrolysis gas was represented by only CH4. Inclusion of tar breakdown reaction appreciably increased the overall heat release due to combustion of its products above the leaf.