They scored two tries, one of them converted, to take a slender 19-18 advantage - a penalty in the 62nd minute gave them more breathing space at 22-18.
Wairarapa-Bush were not done with, however, and a penalty with seven minutes showing on the clock again closed the gap to one point, before South Canterbury made the most of a penalty attempt two minutes further on to take their lead to 25-21.
The last few minutes saw Wairarapa-Bush throw everything but the proverbial kitchen sink at their opposition and a try looked imminent until a fumble from a 5m scrum ended the game, much to South Canterbury's delight and Wairarapa-Bush's frustration.
South Canterbury coach Barry Matthews conceded afterwards his team had been given a whale of a game by the visitors and suggested his team had frozen at times under pressure. But at the same time they had displayed plenty of steel to keep their line intact when Wairarapa-Bush attacked strongly in the final stages.
Lock Joseteki Veikune was outstanding for South Canterbury as were No8 Kieran Coll, flanker Sam Vea and second-five Miles Medlicott, while hooker Andrew Makalio was the standout for Wairarapa-Bush, making several darting runs on attack and also getting through a power of work in defence.
First-five Tim Priest also impressed, coming up with a try from his own charge down and 16pts with the boot. He did though also have 10 minutes in the sin bin after being judged to slap down a South Canterbury pass when they were hot on attack.
Coll, Don Lolo and Frank Havea scored tries for South Canterbury, with Jared Trevathen kicking two conversions and Jason Merrett two penalties. Priest and Paul Tikomainavalu were the Wairarapa-Bush try scorers and Priest added one conversion and three penalties.
Saturday's loss means the end of the 2015 season for Wairarapa-Bush and they have every reason to feel more than satisfied with their efforts, which saw them making the semifinals of the premier section after failing to make even the second tier Lochore Cup semis the previous year.
South Canterbury's opponent in the Meads Cup final next weekend will be Wanganui, who beat Mid-Canterbury 26-11 in Ashburton in their semi-final fixture. Wanganui kicked four first-half penalties.
The Lochore Cup semis saw North Otago thrash Horowhenua-Kapiti 57-12 in Levin and King Country upset Buller 20-6 in Westport.