Adam Dunn belted a three-run homer in the fifth inning to snap a tie and the Washington Nationals never looked back, rolling to a 14-5 victory over the St. Louis Cardinals.

Dunn added a two-run double and Michael Morse went 4-for-4 with an RBI and two runs scored for Washington, which posted its 100th win at Nationals Park in its three-year history.

With two outs and the game even at 5 in the fifth, Roger Bernadina and Ryan Zimmerman singled before Dunn launched a 3-2 offering from Kyle Lohse over the center-field wall for his 32nd home run of the season.

The Nationals put away the game with six runs in the eighth, with Bernadina's two-run homer capping the outburst.

St. Louis, which has lost nine of 13, grabbed a 3-0 advantage in the first inning on Albert Pujols' RBI double and a two-run homer by Jon Jay. Ivan Rodriguez got Washington on the board in the second with a run-scoring single and Dunn highlighted a four-run, two-out rally in the third with a two-run double, giving the Nationals a 5-3 bulge.

Lohse and Felipe Lopez delivered RBI doubles in the fifth to knot the contest before Dunn's decisive shot in the bottom half.

Livan Hernandez (9-9) posted his first win in his last seven home starts despite allowing five runs and eight hits in 6 1/3 innings.

Lohse (2-6) fell to 1-2 since returning from a lengthy stay on the disabled list, surrendering eight runs and 11 hits in just five frames.