A walk power mower having a cutting deck supported upon the ground by a front and rear wheel(s). The mower includes a traction drive system incorporating a bidirectional transmission adapted to propel the mower alternatively in both forward and reverse directions. In some embodiments, the mower may include a single bidirectional transmission (e.g., powering only rear wheel(s) or only front wheel(s) of the mower), while in other embodiments, two bidirectional transmissions may be provided to power both the front and the rear wheel(s). In other embodiments, the mower may include a bidirectional transmission powering the rear wheel(s), while the front wheel(s) may be attached to the deck via a caster assembly.