One of the defining properties of human language is the abundance of potentially unbounded dependencies between elements in a sentence. And yet, how speakers formulate dependencies in sentence production is still poorly understood. Here we examine the timing of verb planning in sentences involving across-the-board and parasitic gap constructions. Using a new task we call the Sentence-Word Interference task, we show that speakers plan the verb of a secondary clause before sentence onset, but selectively when producing across-the-board sentences and not when producing parasitic gap sentences. Based on this timing contrast, we argue that speakers plan verbs predominantly before the production of their dependents, but only when verbs and their dependents engage in both conceptual and direct syntactic relationships. More broadly, the current study suggests that sentence planning is constrained by syntactic relationships that are not reducible to conceptual relationships or to surface word order.