Brandon Saad, Mikko Rantanen, Nathan MacKinnon and Valeri Nichushkin also scored for Colorado, which recorded its first sweep since winning over Vancouver in the Western Conference quarterfinal in 2001.
The Avalanche beat the Blues 20-7 and trailed only 7:12 in all four games. Grubauer stopped 103 of 110 shots in the four games.
“I thought we got a little better as the series went on,” said Colorado coach Jared Bednar. “It was a full 60 minute effort. The first three games, we had a few gaps in our game, things that I didn’t like. Tonight I liked it a lot.
Vladimir Tarasenko scored twice for St. Louis, which was swept away for the first time since losing to the Los Angeles Kings in the second round in 2012.
Landeskog dropped a Samuel Girard shot at 14:53 of the second period to break a 1-1 draw.
“Coming here to a tough building to play and taking two in a row against a desperate team is not easy,” Landeskog said. “I’m glad we did it without giving them any kind of momentum. “
Saad scored from a high lunge shot on a Cale Makar pass just over three minutes earlier. Grubauer got an assist on the game.
Landeskog finished with two goals and six assists recording a point in every game of the series.
“You break down every game and I think the score hasn’t really been indicative of how the series has been,” Landeskog said. “It was very tight, it’s hard to check and it wasn’t easy. Coming here to a tough building to play and taking two in a row against a desperate team is not easy. “
Landeskog said the Avalanche used a pre-series boast from St. Louis captain Ryan O’Reilly as motivation. O’Reilly claimed the Blues would win the series.
“Yes, that’s right,” Landeskog said. “It was a contested series. “
Rantanen whipped a wrist shot past Jordan Binnington with 15:40 left in the third period to push the lead to a 3-1. Rantanen broke in on a 2-1 and took a pass from teammate MacKinnon.
Tarasenko converted on a breakaway pass from O’Reilly for a 1-0 lead at 5:07 of the second period. It was Tarasenko’s first goal since April 26. He added a power play goal with 11:21 left to reduce the deficit to 3-2.
MacKinnon and Nichushkin added goals into an empty net in the last minute.
Binnington made 29 saves.
Tarasenko was not satisfied with his team’s efforts.
“It’s embarrassing to always lose in the playoffs,” Tarasenko said. “The answer is there are no excuses. We don’t fight enough. “
St. Louis coach Craig Berube said injuries, especially at the Blues’ backline, were a factor in the series, but he wouldn’t offer that as an excuse.
“They’re the best team for sure,” said Berube. “We have to improve, we have to improve. “
Colorado has won nine of the last 10 playoff games against St. Louis, including seven in a row.
The Avalanche scored six goals in an empty net in the series, including two in a 6-3 win in Game 2 and two on Sunday.
Colorado C Nazem Kadri is in Game 2 of an eight-game suspension after hitting Justin Faulk in Game 2. It is the sixth suspension of his career. He is appealing the suspension, with the NHL Players Association filing it on Sunday night on behalf of Kadri.
Avalanche: C Alex Newhook started in the first half and didn’t come back after a Steven Santini hit.
Blues: D Justin Faulk, Robert Bortuzzo and Vince Dunn did not play. Dunn has missed the last 15 games with an upper body injury. Faulk and Bortuzzo each suffered head injuries in Game 2.