This article addresses the morphological constraint on the ‘formulaic frame’ be-sure-and-v (Be sure and wear flowers in your hair!), whose idiomatic reading disappears in inflected uses (*She was sure and wore flower in her hair). This constraint also applies to certain verbal patterns (go/come-v, try-and-v) and is at least probabilistic for others (wait and see, go-and-v). A recent usagebased approach suggests that the so-called Bare Stem Condition follows from the semantics of the affected patterns, which are schematically non-assertive and thus functionally inappropriate for use in inflected, assertive environments. The same can be shown to apply to hortative be-sure-and-v, suggesting that the morphological behaviour of both verbal and adjectival pseudo-coordination have the same underlying functional-semantic constraint motivation. Supporting evidence comes from the status of be-sure-and-v relative to instantiations of the pattern: rather than being an idiosyncratic, isolated idiom, be-sure-and-v is a subtype of a moderately productive be-adj-and-v construction (be honest and admit, be patient and wait). Be-adj-and-v shows many of the characteristics of other pseudo-coordinated constructions, including the combination of semantically coherent slots fillers (flexible-adapt, glad-rejoice) and the asymmetric framing of single events. Methodologically, the article showcases how Collostructional Analyses can be used as diagnostic tools to identify (sub)types and slot-filler consistency in a bottom-up fashion, separating schema instantiations from syntagmatic ‘noise’ (i.e., the compositional adjectival predicate, My raspberries are ripe and taste delicious). Thus, the method identifies (and confirms) be-sure-and-v as the morphological, semantic, and statistical prototype of the more general schema.