We have added support for associative unification to Maude 2.7.1. Associative unification is infinitary, i.e., there are unification problems u= ?v such that there is an infinite minimal set of unifiers, whereas associative-commutative unification is finitary. A unique feature of the associative unification algorithm implemented in Maude is that it is guaranteed to terminate with a finite and complete set of associative unifiers for a fairly large class of unification problems occurring in practice. For any problems outside this class, the algorithm returns a finite set of unifiers together with a warning that such set may be incomplete. This paper describes this associative unification algorithm implemented in Maude and also how other symbolic reasoning Maude features such as (i) variant generation; (ii) variant unification; and (iii) narrowing based symbolic reachability analysis have been extended to deal with associativity.