The Cavaliers’ LeBron James plows into the Celtics’ Leon Powe in the second half. James, the NBA’s regular-season scoring leader, ran into waves of Boston defenders again last night, scoring 21 points but shooting only 25 percent.

The Providence Journal / Glenn Osmundson

BOSTON –– If only the Boston Celtics could take Lucky the Leprechaun, their dancing girls and Gino the Dancing Guido to Cleveland for the weekend.

Those comforts of home paved the way to a dominating 89-73 win last night at TD Banknorth Garden and staked the Celtics to a 2-0 lead over the Cleveland Cavaliers in their best-of-seven series. Now it’s time to see if the stranglehold defense, energetic running game and timely offense can travel to Ohio for Game Three tomorrow night.

The Cavaliers have to hope that the Celtics’ shaky road playoff efforts during the first round in Atlanta continue because they didn’t do much against the Celts here. In two games, the Cavs shot 33 percent and could never find an offensive groove. Their chief bricklayer has been LeBron James. The NBA’s leading scorer in the regular season, James has shot 8-for-42 in the series. Last night, James led the Cavs with 21 points but hit just 6 of 24 shots.

“Home court has been good for us,” said James. “We have to keep our heads up and we just have to start knocking down shots. We missed open jumpers and layups that you have to knock down.”

Unlike Game One when both teams struggled offensively, Boston was much improved last night. Paul Pierce bounced back from a four-point effort to lead the Celts with 19 points. Ray Allen had a goose egg in the first six quarters of the series but exploded for 16 points in the second half last night.

Joining James in double figures for the Cavs was center Zydrunas Ilgauskas with 19 points and Wally Szczerbiak with 13.

“They played well. They did what they were supposed to do, they held onto home court,” said Szczerbiak, a former Celtic. “Now we have to go back and regroup because that second half was not Cavalier basketball. We let the crowd get to us a little bit. We didn’t execute. They came at us, they smelled blood and they went right for the jugular.”

The game actually started off poorly for the Celtics. With James moving the ball well and continually finding Ilgauskas, the Cavs sprinted to a 10-2 start with the big man scoring his team’s first eight points. Ilgauskas made his first six shots and led the Cavs to a 24-17 lead after 12 minutes.

But the entire Cleveland team appeared a bit dazed in the second quarter. With Boston trapping the ball at every turn and sprawling to the floor for every loose ball, the Cavs quickly lost their lead. Several reserves led a game-changing 19-3 run to take control. James Posey nailed a 3-pointer, Leon Powe tipped in his own miss and P.J. Brown knocked home a 16-footer to start the run. When Posey picked off a James pass and flew down the floor for a jam, the Celtics grabbed the lead for good, 28-27.

The Celts kept humming along and led 44-36 at the half. James missed all five shots he attempted in the second quarter and was shooting 3-for-13 at the break. His teammates weren’t much better. The Cavs made just two of their 17 second quarter shots (12 percent) and were nonexistent off the boards where Boston held a 19-8 advantage in the second quarter.

“The second unit came in and gave us energy, effort,” said Celtics coach Doc Rivers. “We didn’t have energy to start the game but the second unit saw that. We didn’t make any defensive adjustments.”

Cleveland needed a big push to start the third quarter but the Celtics were the ones who did all the pushing. The Cavaliers were outscored 26-15 as Boston’s Allen finally got hot as he made a layup, sank two free throws and went on to score 11 third-quarter points. Celts led 70-51 after three and didn’t let the Cavaliers within 15 points the rest of the way.

The Cavs fell behind Detroit 2-0 in last year’s Eastern Conference finals and rebounded to take the series and advance to The Finals. They hope a return home can not only shake their game up but also open some holes in the Celtic defense.

“Boston should be confident,” said Cavs’ coach Mike Brown. “They have great stars, but this is what a series is all about. It is not over until someone wins four games. Half our team has been in this situation before. We know that Game Three is a separate entity. We will get energized by our crowd and try to get a win.”

kmcnamar@projo.com