First five Matt McGahan, looking briefly more like the confident No 10 who won the Bronze Boot from the 2010 trans-Tasman schools international, broke some weak tackles to plough over for the opening try and a 10-0 lead.
But soon afterwards Garden-Bachop started swinging his right boot to telling effect, even as the Lions struggled to rediscover their attacking mojo.
The breakdown was messy, sides wrestling and kicking the ball through making for an untidy spectacle.
Harbour were standing too deep on attack and not commanding field position, which ultimately told. But they were looking fine when lock Brandon Nansen shed Greg Foe and burst through a hole to score between the uprights for a 17-12 advantage. The visitors should have scored not long after that when a crosskick landed in the grateful arms of former Wellingtonian Afa Fa'atau on the wing. But he was not able to link and another chance went begging.
In the final moments the Lions, even with a rookie prop on (Alex Fidow) and several other youngsters, maintained their cool and banked the points. Then they should have gone straight to the bar and shouted Garden-Bachop whatever he wanted all night long.
Harbour skipper James Parsons lamented a lack of composure in the clutch and felt his side needed to use the width that was effective in the first stanza.
"We had plenty of opportunities out there, but it was similar to last week (when they lost to Waikato in a Shield clash). Hopefully we can learn from it for Manawatu next week," said the two-test All Black.
Wellington captain Brad Shields knew his team were not quite in synch and still coming to terms with the new rules.
"We're about 10 percent off. North Harbour is a good team and it was hard to beat them. She's still a bit tricky with the new rules, but we're all learning and hopefully we'll have it by the end of the round," Shields said.
Wellington are in Pukekohe next Friday night for the Jonah Lomu Memorial Trophy clash with Counties Manukau, while North Harbour host Manawatu next Saturday.
Wellington 21 (J. Garden-Bachop 7 pens)
North Harbour 17 (M. McGahan, B. Nansen tries; M. Vaega 2 cons, pen)
HT: 10-9 North Harbour