This paper investigates how children figure out that functional modals like English must and Dutch moeten 'must' can be used to express different 'flavors' of modality: epistemic, deontic, bouletic, and so on. The existing acquisition literature shows that children produce functional modals with epistemic meanings up to a year later than with root meanings, suggesting that they may initially fail to realize that these modals can express epistemic meanings in addition to root. We conducted a corpus study on English and Dutch child-directed speech to examine how modality is expressed in speech to young children, to investigate the ways in which the input may help or hinder learners uncover the multiple flavors functional modals can express. Our results suggest that the way parents use functional modals may obscure their polysemy: modals are mainly used either with a root or an epistemic flavor, with an overall strong bias towards root uses. This is even more so in Dutch than in English. Yet, children eventually figure out modal polysemy. To investigate how the linguistic input might help, we explore a distributional difference between roots and epistemics that could give away epistemic flavor, concerning modals’ temporal properties, which we track by the aspectual properties of the modal's prejacent. We show that the aspectual differences are well reflected in the distribution of root and epistemic flavors of functional modals in both English and Dutch. However, the strong usage bias towards root meanings may lead to a weakened signal, suggesting the cue will be useful only if learners expect flavor-based constraints, and use them in combination with cues stemming from the situational context.