Davey Johnson isn't shaving his scruffy beard, even after the Washington Nationals finally put on the offensive show he was longing to see.

Adam LaRoche homered twice and drove in four runs, and the Nationals barreled past the Baltimore Orioles 9-3 Tuesday night.

LaRoche, Tyler Moore and Roger Bernadina connected off Orioles rookie Kevin Gausman (0-2). LaRoche added a solo shot in the eighth off Troy Patton.

It added up to Washington's highest-scoring performance since a 10-3 win over Miami on April 15. The Nationals hadn't scored more than seven runs in 29 games since April 25.

The 70-year-old Johnson began growing the beard last week and said he wouldn't shave until the Nationals broke out of their hitting slump. Now it appears he won't shave for fear of jinxing a team on a roll.

"It was great," Johnson said of the hitting attack. "Some guys that usually take two or three strikes went up there and hit line drives."

And then, fondling his gray beard, he added, "Maybe this is working."

Addressing the suddenly hot topic of Johnson's beard, Moore said, "It looks pretty bad, doesn't it? I hope he looks like Santa at the end of the year if we keep winning."

Washington built a 7-3 lead in the fourth inning for right-hander Nathan Karns in his major league debut. But Karns couldn't make it out of the fifth.

Karns gave up three runs, five hits and two walks in 4 1-3 innings. He was alternatingly sharp and shaky, but decent enough to earn another chance.

"Nathan Karns did good, so he's going to come back and pitch Sunday," Johnson said. "I thought he handled himself well. Good start against a good hitting ball club. I know he was nervous but I like the way he went after the hitters."

Selected in the 12th round of the 2009 draft, Karns never before pitched above the Double-A level. The 25-year-old was 4-2 with a 4.60 ERA this season in nine starts for Harrisburg of the Eastern League.

The start of the game — and Karns' big league debut — was delayed by rain for 1 hour, 21 minutes. He didn't care.

"The rain delay didn't bother me at all," the rookie said. "Now the first one is out of the way I can just build off of that."

Zach Duke (1-1) followed Karns with 1 2-3 innings of perfect relief.

Chris Davis hit his major-league leading 17th homer for the Orioles, and J.J. Hardy also went deep. But Baltimore's franchise-record run of scoring at least five runs in 10 straight road games ended.

After allowing four runs in five innings against Toronto last Thursday in his major league debut, the 22-year-old Gausman digressed in his second appearance. The right-hander gave up seven runs and eight hits in four innings with one walk and no strikeouts.

Gausman, the No. 4 pick in the 2012 draft, is toting an unsightly 11.00 ERA and opponents are batting .385 against him.

"Pitching in the big leagues is hard. He's got the talent to do it and eventually he will," Orioles manager Buck Showalter said. "I look forward to it being next time out. He knows mistakes get magnified here. But it's part of the process."

Washington pulled away with a four-run fourth. LaRoche drew a leadoff walk, Moore hit his second homer in 81 at-bats this season, and Bernadina followed with his first long ball since Sept. 28.

"After Bernadina and Moore went deep you want me to shave? I can't shave right now," Johnson said with a grin.

With two outs, Denard Span added an RBI double to make it 7-3.

Early on, with his fastball hitting 97 mph, Karns retired the side in order in the first inning on three groundouts.

"I just wanted to get out there and throw strikes, work with getting the hitters out, and it worked out to my advantage," Karns said.

Gausman, in contrast, struggled at the outset. After Span hit a scorching grounder that was gloved by Davis at first base and turned into an out, Steve Lombardozzi and Ryan Zimmerman both singled before LaRoche drove a 2-0 pitch into the center-field seats.

Baltimore closed to 3-1 in the second on an RBI double by Matt Wieters. But with one out and runners on the corners, Karns struck out Yamaico Navarro and Gausman.

In the fourth, Davis lined a 1-2 pitch into the Washington bullpen beyond the right-field wall. Two batters later, Hardy homered to left into the Orioles' bullpen to knot the score at 3.

NOTES: The Nationals played a second straight game without OF Bryce Harper (knee), and Johnson acknowledged, "I probably was being optimistic thinking he could DH over in Baltimore (on Wednesday and Thursday). It's probably not looking good for that." ... Washington 2B Danny Espinosa, who has been sidelined since May 22 with a fractured bone in his right wrist, hopes to return Wednesday. "The strength is fine. It's just the stiffness," Espinosa said. ... The Nationals have homered in 73 straight series,, the longest active streak in the majors. ... Chris Tillman will take the mound for the Orioles on Wednesday night at Camden Yards against Washington's Jordan Zimmermann, who is seeking his ninth victory. ... Baltimore's Nick Markakis had his 12-game hitting streak snapped.