Wellens touched down with four scores in a 16 minute period after half time. Until then, the visitors were well in the game, holding Catalans to a 19-6 deficit at half time.
St Helens coach Daniel Anderson was full of praise for Wellens. He said: "To get four tries is a wonderful effort – he produced performances like that all the time last season and that's why he was crowned Man of Steel.
"His support play was terrific but his team-mates helped him as well, although overall we were a mixed bag.
Kiwi prop Jason Cayless, Leon Pryce and Keiron Cunningham grabbed four pointers, with Matt Gidley scoring a fourth try before half time. Paul Sculthorpe landed one goal and Sean Long slotted home a drop goal on the stroke of half time.
The Dragons couldn't handle Saints after the break, with Wellens taking over the show. Dmitri Pelo stopped the rot momentarily with a 51st minute try, but 3 more scores from Wellens, and further scores from Maure Fa'asavalu and Francis Meli increased the advantage.
Both coaches were full of praise for their counterparts at the final hooter.
Catalans Dragons coach Mick Potter said: "No side can live with St Helens when they're in that kind of mood.
"We could have done a few things a bit differently but it's difficult to handle Saints at the best of times."
Anderson added: "It's been good to get six points out a very tough period and there was definite patches of fatigue.
"At the end of the day, we were the better side but Catalans deserve a lot of credit for the way they performed."
St Helens remain top of Super League following 7 straight wins and Potter added: "They're the outstanding team in Super League and it's up to the likes of Bradford, Leeds and Hull to try and stop them."