The Taieri loose forward trio of Erik Vaafusuaga, Jeremy Corliss and Callum Bissett played a key role in Taieri's win at Peter Johnstone Park.
They hunted as a unit and their marauding play turned the initiative in Taieri's favour when Green Island was dominating the game in the opening 20 minutes.
The Green Island backline was a more effective unit with first five-eighth Dean Moeahu giving the line speed.
Haua Fleming was dangerous on the burst and scored the first try after 20 minutes to give Green Island a 10-0 lead.
Fullback Tamati Tamakehu was safe under the high ball and dangerous on the counter-attack.
Taieri's strength was in the forwards and it was Vaafusuaga who grabbed the initiative with a strong driving run after 25 minutes.
Corliss closed the gap to two points at the break when he attacked the line after his team won the ball at the breakdown after 39 minutes.
He scored wide out after a 15m driving run.
Bissett not only tackled effectively but also gained valuable ball at the back of the line-out.
He won the ball that led to Taieri's second try after 28 minutes in the second spell.
Experienced first five-eighth Ricky Stewart sped through the gap and Danny Loli was on hand to score under the bar to give Taieri a 21-13 lead.
Stewart landed four of his five shots at goal and his generalship was of a high standard.
The Green Island scrum was pushed around until the Short brothers came on as substitutes in the front row and started to exert pressure.
Taieri 21 (Jeremy Corliss, Danny Loli tries; Ricky Stewart conversion, 3 penalty goals), Green Island 18 (Haua Fleming, Brent Short tries; Shannon Young conversion, 2 penalty goals).
Half-time: Green Island 13-11.
Referee: Todd Pullar.
