What is the best way to account for phonetic surface variants resulting from a productive vowel alternation? How does the lexical representation of such vowels look like? This paper proposes a single representation for the present tense root vowel in German irregular (strong) verb forms which show an alternation between [a]/[ε] and [e]/[i] in the corresponding person/number realizations. The claim is that the alternating vowels do not have a place of articulation feature specification in their underlying form. Evidence for this feature-based approach comes from two crossmodal immediate repetition priming experiments which compare irregular (strong) with regular (weak) verbs. The latter do not have any root vowel alternations.