The 19-year-old imposed himself on the game from the start and provided assists for both goals, for Cammy Kerr in the 40th minute and Marcus Haber ten minutes from time.
The forward was only denied a goal himself by a good stop by Craig Samson after weaving his way into the Motherwell box.
The teenager’s skill was a joy to watch but his decision-making and timing of pass were equally impressive, none more so than when he cut the ball back for Haber to slot home his first goal for the club.
Hartley has been looking for a way to replace the goals and guile of Kane Hemmings and Greg Stewart and he may have found it after linking Wighton with recent signing Haber.
“I felt the two front players make a big difference for us,” Hartley said. “Big Haber has taken the ball in really well and we have changed where Craig is playing. He was excellent.
“He has been around the squad for the last three or four years and there was a lot of expectation on his shoulders. I have had to be really patient with him. People were telling us when to play him and get him in the team but we have been patient.
“But it’s his time now, I think. We lost two key players in the front line in Hemmings and Stewart but Craig has definitely got everything. He is an outstanding talent, really good to work with. I think he can only get better but he now has to establish himself in the team.”
Motherwell struggled to get back in the game after Kerr tucked away a rebound from Wighton’s shot after dispossessing Scott McDonald himself on the halfway line.
But they left Dens Park with a sense of injustice after Dundee goalkeeper David Mitchell appeared to carry the ball well over his line when catching McDonald’s cross in the 21st minute. Referee John Beaton and assistant Ross Haswell both played on.
Manager Mark McGhee told Motherwell’s YouTube channel: “Not to be given the goal is ludicrous. It’s a shocking and scandalous decision.
“But then we go on to concede a goal which was as big a crime as the referee and linesman were guilty of.”
McGhee now goes on Scotland duty but he has ordered his players to begin focusing on the visit of Partick Thistle on 19 November.
“I’ve asked them to make sure they start immediately to prepare for the Thistle game, not to let themselves drop, to roll up their sleeves, work hard together and stay fit,” he said.
“It’s 21 games now to the split and that’s what we have got to target. It’s still a very tight league. But we know we have to do better than that. We knew the team that gets the first goal is likely to win the game.”