The competition between 11 societies, involving about 80 people, has been held since 1977 and was inspired by rose breeder Sam McCready, who was also a big rugby fan.
The societies compete over 12 classes, the team with the most points winning.
Mr McCready presented the Rose Ranfurly Shield to this year's winner, Marlborough, which narrowly beat last year's winner North Otago, with Westland finishing third.
Organiser of the event Val Clarke said each society was allowed one entry in each class.
Roses were picked on Friday morning, allowing society representatives time to travel to Oamaru, where their selections were judged on Saturday morning by national judge Eileen Wilcox.
Heavy rain two weekends ago had made it more difficult for local growers to select top blooms.
The weekend started with a "meet-and-greet" on Friday night, with judging conducted on Saturday morning while competitors went on a bus tour.
The roses then went on public display.
There was a Victorian-themed dinner on Saturday night, at which the winners were announced, and representatives enjoyed morning tea yesterday before they left Oamaru.
Results of other competitions (not counting towards the shield):-Bucket of roses: South Canterbury; Canterbury 2000 Trophy (bucket of mini roses): North Otago; vase of David Austin roses: South Canterbury; Victorian tussie mussie: North Otago.
