The objective of this study was to examine the competitive sorption-desorption behavior of two triazine herbicides (atrazine and ametryn) to better understand their mode of interaction with plant cuticular matter. Both sorbates exhibited significantly higher affinity to the cutin fraction than the bulk or dexaxed cuticular sheets. Moreover, sorption isotherms with the cutin exhibited more linear behavior than the isotherms obtained with the bulk cuticle. The lower sorption affinity of both solutes obtained with the bulk cuticle and their nonlinear isotherms suggest a more rigid structure of the bulk cuticle, which reduces the sorption affinity of its major component, the cutin (71% by weight). In the bi-solute system, atrazine sorption affinity to the bulk cuticle was reduced by 15% and sorption linearity increased. In the case of cutin, sorption affinity of atrazine did not change due to the presence of ametryn. The desorption behavior of atrazine was also affected by the presence of ametryn. While very little desorption hysteresis was observed for atrazine with the bulk cuticle in the single-solute system, significant hysteresis was observed in the bi-solute system. In contrast, for the cutin, the KFoc values calculated for atrazine in single- and bi-solute systems were statistically similar. This study demonstrates that cutin is the major cuticular constituent for sorption of triazine herbicides. This biopolymer affords a linear single-solute isotherm and no competition behavior which resembles that of a rubbery-like polymer. The bulk cuticle is probably less flexible and therefore exhibited a nonlinear single-solute isotherm, significant competition and major desorption hysteresis in the bi-solute system. This suggests that the pectin and wax materials are strongly linked to the cutin structure which is therefore less flexible in the bulk cuticle than the isolated cutin fraction.