Show manager and Dunedin Dahlia Circle president Stuart Brown said the show had received about 900 entries, but that would have been considerably fewer if the rain had come earlier and damaged competitors' prize blooms.
The show was held at Forbury Park at the weekend and hosted by the Dunedin Dahlia Circle.
Growing flowers for competition was "a very serious business", and some people would rush out to put umbrellas over their plants to protect them if it rained, he said.
Flowers had to arrive at the competition venue in top condition and be transported carefully so they did not bang against each other or anything else.
Rain-marked, bruised or damaged flowers would lose points when they were judged.
Dahlias were increasing in popularity, and he believed people were attracted to their bright colours, Mr Brown said.
The blooms range from giant-sized, measuring about 30cm in diameter, to small pompom flowers.
The South Island show was last held in Dunedin in 2002.
South Island dahlia show results. - Champion of champions: V. Crichton (Invercargill), Hamari Accord; champion bloom open: V. Crichton, Hamari Accord; champion vase open: W. and B. Andrew (Timaru), Pam Howden; champion bloom intermediate: J. Waller (Invercargill), Hamari Accord; champion vase intermediate: P. and J. Gibbison (Blenheim), Tui Avis; champion bloom novice: S. and B.
Cornwall (Ashburton), Janal Amy; champion vase novice: A. Brown (Invercargill), Lady Kerkrade; champion bloom from first time exhibitor: M. Penty (Dunedin), Rhanna Tammy; host trophy: W. and K. Jack (Invercargill).
