Otago keeper Oswaldo Rodriguez spilled a strong shot in the first minute, for Louis Fenton to dart in and score the first of his hat trick.
Mike Eager doubled the score shortly afterwards.
Coach Richard Murray hoped his side could hang in until the second half and harness wind advantage, but another Wellington score just before the break gave coach Matt Calcott's team a three-goal cushion.
Otago played better in the second spell, as Harley Rodeka continued his good form with carving runs past Wellington defenders. Striker Ant Hancock was tightly marked, yet did wriggle free with only keeper Scott Basalaj to beat but dragged his shot wide midway in the half.
Better known for forgetting his red cards and having to borrow some from a linesman last time he visited Dunedin, referee Mirko Benischke carried a few this time.
The official yellow-carded Otago's Aajay Cunningham, Sam Mepham and Matt Joy, then double-yellowed Rodeka, who had to leave the field late in the match.
Benischke also booked Wellington's Dakota Lucas, former Dunedin Technical player Cam Parkin and Johny Raj, as well as awarding two penalties from which Wellington scored.
Yet this match was no bloodbath, and the two young sides played incisive attacking football.
Wellington built on its early two-goal lead and oozed confidence. Otago came back off the ropes and grafted back into contention, but conceding two penalties further eroded confidence.
Wellington coach Calcott was obviously pleased to have reached the White Ribbon final.
"Our lads played with the tempo and pace we have been aiming at all season," he said.
Players he mentioned in dispatches were hat trick hero Fenton, and other scorers Eager and Lucas, with former Caversham player Patrick Fleming commended for effective running in central midfield.
Otago coach Murray was disappointed at his team's jaded form, which only improved in the second half, when the scoreline made a fightback near impossible.
Rodeka was irrepressible, and Joy and Prattley were steady.
New Zealand under-23 international Prattley scored Otago's goal from another penalty awarded by Benischke.
Other Otago players had good moments, but so often, after doing good things, they gave the ball away and put themselves back under pressure from the hungry Wellington side.
Possibly the happiest Otago player was Mosgiel's Matt Brook, who did not get off the bench, but had confirmation that he has initially been accepted for a coaching job in Perth. Then the young defender is off to Hawaii University where he will take up a football scholarship.
ASB Premiership
The scores
Wellington - 6
Louis Fenton 3, Mike Eager 2, Dakota Lucas
Otago United - 1
Tristan Prattley
Halftime: Wellington 3-0
