Jackson struck out nine as the Cubs and Astros played to a 6-6 tie in 10 innings in an exhibition game.
Jackson plunked the first batter he faced, and leadoff hitter Jose Altuve moved up when Brett Wallace followed with a walk. Chris Carter then hit a two-run double with one out before Jackson struck out two straight to end the inning.
Houston's Marwin Gonzalez hit an opposite-field, three-run homer in the second before Jackson retired nine of the next 10 batters, striking out seven of them. He gave up five hits and was replaced by James Russell for the fifth inning.
His nine strikeouts were one more than he'd had in his previous five spring starts.
"I think I just sped up my pace a little bit," Jackson said of the difference between the first two innings and the second two. "Early on I felt I was a bit deliberate. After the home run, start over and get in the groove and pick up the pace a little bit."
Jackson signed a $52 million, four-year deal with Chicago over the winter. He allowed just four runs in his first four starts this spring before yielding 10 in his last two.
"Clearly you want good results, but the results are not always there," Jackson said. "But you come out and you feel like you are ready to go, and I felt I was ready to go today. As a pitcher, you just want to stay more consistent all around."
Cubs manager Dale Sveum was unhappy with the length of the game.
"It was long. Four hours," he said. "Not what you really want in a spring training game leading up to a day game."
He also didn't like how Jackson started the game, but was pleased with how he recovered.
"It's one of those things where, kind of a spring training-type atmosphere, nobody in the stands, and all of a sudden we gave up some runs . and then we started pitching," he said.
Houston starter Alex White gave up three runs and three hits in one inning. White, who will start the season in the bullpen, has allowed 12 hits and seven runs in his last two outings.
Manager Bo Porter said the right-hander had some discomfort in his throwing elbow and would undergo tests on Saturday.
"He was only going to throw two innings tonight anyway," Porter said. "So it made more sense just to get the relievers in the game. We had a bunch of relievers that needed to throw, so we just went ahead and got him out of the game."
White said the discomfort has been nagging him for a couple of weeks.
"In the bullpen today I was a little stiff, but once I got in the game I felt OK," he said. "I had a good breaking ball tonight."
These teams wrap up the exhibition season on Saturday when Chicago left-hander Travis Wood opposes Brad Peacock. ... Astros SS Carlos Correa, the top overall pick in the 2012 draft, will start on Saturday. ... Houston Texans defensive end J.J. Watt, the NFL's defensive player of the year, took batting practice before the game. He had trouble getting going, but ended up hitting five home runs. "I started off super slow, but then they started to get the pitches a little bit higher and I had a little success at the end," he said. "But I'm disappointed ... if we would have kept going I would have had a few more." Watt, who will throw out the first pitch before the Astros' opener on Sunday night, said he threw a bullpen session recently to prepare for the job. "I threw about 45 pitches, so I will be much more ready for my first pitch than I was for the batting practice today," he said.