Houston took a 1-0 lead in the second inning on Johnson's homer to left field on an 0-1 pitch from Nats left-hander John Lannan, who pitched five innings and allowed two runs on two hits.
But the Nationals went on to take a significant lead. With right-hander Jordan Lyles on the mound in the bottom half of the second, Jason Michaels hit into a fielder's choice, scoring Chad Tracy, who had singled earlier in the frame. In the next inning, Washington added two more runs on an RBI single from Tracy and an RBI double from Wilson Ramos.
The Nationals scored three more in the fifth, highlighted by Roger Bernadina's two-run homer off left-hander Kevin Chapman. Bernadina finished with two hits and is batting .279 this spring.
The Astros scored their last two runs of the game in the seventh inning, when Brandon Barnes hit a two-run homer off lefty Ross Detwiler.
Up next: Left-hander Wandy Rodriguez, who's expected to be the Astros' Opening Day starter, makes his fourth start of the spring when the Astros return home to face the Detroit Tigers at 12:05 p.m. CT at Osceola County Stadium on Tuesday, live on Gameday Audio. Rodriguez has allowed nine earned runs in his previous two starts and is looking to pitch deeper into the game.
Bill Ladson is a reporter for MLB.com and writes an MLBlog, All Nats All the time He also could be found on Twitter @WashingNats. This story was not subject to the approval of Major League Baseball or its clubs.