Matt Holliday had three hits for the Cardinals, who had their NL Central Division lead over Pittsburgh trimmed to one game. The Pirates beat San Diego 10-1 on Thursday.
D. J. LeMahieu started the winning rally with a one-out single to right. Dickerson then drilled a line drive into the right-field corner as LeMahieu rounded the bases. The relay from second baseman Matt Carpenter beat LeMahieu but catcher Yadier Molina couldn't control the ball as LeMahieu crawled to touch home.
It was Dickerson's second triple of the game and sixth of the season.
In the first inning, Helton tagged out Carpenter at first with the hidden-ball trick. After Roy Oswalt threw to first, Helton feigned a throw back to the mound and tagged Carpenter when he stepped off the bag to end the inning.
The Cardinals loaded the bases in the 15th but Pete Kozma hit into a double play to end the inning.
It capped a long day in which the teams traded late-game rallies.
Helton, who struck out with the bases loaded to end Wednesday's game, turned on Edward Mujica's fastball Thursday, sending an 0-1 offering into the Rockies bullpen to lead off the ninth and tie it at 6-all.
It was Mujica's fourth blown save in 41 chances.
Holliday hit his former team hard, going 8 for 21 with a home run, four walks and four RBIs in the series. He reached base in six straight at-bats Thursday and was poised to be the hero with his RBI single in the ninth before Helton tied it with his 14th home run of the season.
It was part of a back-and-forth that saw the Cardinals rally from four runs down but blow two late leads.
Tony Cruz doubled off the wall in left to make it 4-3.
Holliday tied it at 4-all with an RBI single in the fifth.
David Freese gave the Cardinals a 5-4 lead in the eighth with an RBI double to center, but Colorado tied it in the bottom of the inning on Dickerson's two-out triple.
Helton helped the Rockies take an early lead with a leadoff double in the second, his 588th career two-bagger. He moved to third on Charlie Culberson's infield single and scored on Yorvit Torrealba's blooper to right.
Culberson scored on a double play to make it 2-0.
Tulowitzki's two-run homer in the third made it 4-0. It was his 23rd of the season.
NOTES: Cardinals 1B Matt Adams (right elbow soreness) did not start but came into the game as a defensive replacement in the eighth. He singled in the ninth and was replaced by a pinch-runner. ... Rockies OF Michael Cuddyer (left wrist, forearm) was out of the lineup but hopes to play Friday. ... RHP Shelby Miller (14-9) will open the Cardinals' weekend series in Milwaukee on Friday. ... Colorado righty Jhoulys Chacin (13-9) will start the first game of Colorado's series against Arizona on Friday.
Link to box score: Colorado 7, St. Louis 6 (15 innings)
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