He looked in control at 3-up after 13 holes against Omanu Golf Club member and 2016 champion Sisson only to lose a ball off the tee on the 14th.
Reedy won the 15th with a par to be dormie-3-up but lost 16 to a par, then three-putted 17 to lose that hole as well.
On the par-4 18th, Sisson missed the fairway but hit an impressive shot from the practice area on to the green about 25-feet above left of the hole.
Reedy, from the middle of the fairway, put his approach four feet short of the green.
Sisson was expecting he would need to sink his birdie putt to send it to extra holes. The 74-year-old didn't get a chance.
Reedy, off a +3 handicap, was favoured to win the title from the start. But he was the first to admit every match was hard work and he took his hat off to the quality of all his opponents.
Sisson was no exception. His history includes Freyberg interprovincial and masters appearances and the highlight of his career — making the NZ senior team for the Asia Pacific senior championships in India, where he placed second individual overall.
He is also a member of the age-breaking club, having shot his age 21 times. The first of those was at Omanu at the age of 69, when he had six consecutive birdies in a back nine holes of 29 for a 66 off the stick.
Reedy joined an elite list of NZ vet champions, including Poverty Bay's Bowser Toogood who won it in 1968 and 1969, two years before Reedy was born.
Locals claimed titles in two other men's divisions.
Richard Foon gave himself a belated 60th birthday present in his first NZ vets tournament by beating Tene Goldsmith 3 and 2 in an all-Poverty Bay senior reserve final.
Park member Barry Cox had a classic battle with Poverty Bay's Bill Simpson in the intermediate reserve final. Simpson won 16, 17 and 18 to force extra holes but Cox held his nerve on the 19th to avoid clubhouse “choke” jokes. Kit Goldsmith, like older brother and Poverty Bay clubmate Tene, had to settle for runner-up. He lost on the 19th to Hawke's Bay's Peter Johnston.
Ray Skiffington, of Cambridge, defeated Peter Holt, of Shandon, in the junior final.
Home-course player Marg Colebourne dominated the net in the 20-strong women's 72-hole strokeplay competition.
Colebourne's total of 283 (68, 70, 72, 73) was 14 shots ahead of the runner-up. The quality of the course, particularly the greens, received high praise from all players.