Addison has recently started dating Sam (Taye Diggs) but Walsh told TV Line that she will be eager to start a family.
"She's getting to the point of, 'Oh my God, time's up! Let's do this!'" she said. "And yet they've only been dating for a few months, and he's got a grown child, a grandchild and an ex-wife."
However, Walsh added: "When women want a baby, they're pretty tenacious."
Private Practice continues on Thursdays at 10/9c on ABC.