Korean subject honorification and Korean negation have both affixal and suppletive exponents. In addition, Korean negation has a periphrastic realization in- volving an auxiliary verb. By examining their interaction, we motivate several hypotheses concerning locality constraints on the conditioning of suppletion and the insertion of dissociated morphemes (‘node-sprouting’). At the same time, we come to a better understanding of the nature of Korean subject honorification. We show that Korean honorific morphemes are ‘dissociated’ or ‘sprouted,’ i.e., introduced by morphosyntactic rule in accordance with morphological well-formedness constraints, like many other agreement morphemes. We argue that the conditioning domain for node-sprouting is the syntactic phase. In contrast, our data suggest that the condi- tioning domain for suppletion is the complex X0, as proposed by Bobaljik (2012). We show that the ‘spanning’ hypotheses concerning exponence (Merchant 2015; Svenonius 2012), the ‘linear adjacency’ hypotheses (Embick 2010), and ‘accessi- bility domain’ hypothesis (Moskal 2014, 2015a, 2015b; Moskal and Smith 2016) make incorrect predictions for Korean suppletion. Finally, we argue that competition between honorific and negative suppletive exponents reveals a root-outwards effect in allomorphic conditioning, supporting the idea that insertion of vocabulary items proceeds root-outwards (Bobaljik 2000).