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Mover and shaker … Costa Georgiadis has given Gardening Australia a shot in the arm, increasing audience figures by 5 per cent this year.

THIS year will be remembered for many things - the transit of Venus, the discovery of the Higgs Boson particle, and, if the Mayans were right, the end of the world on December 21. But for Australian gardeners the really big news came with the arrival of Costa Georgiadis as the host of ABC TV's long-running Gardening Australia program.

With his windmilling arms and superabundant facial hair, Georgiadis shook up a much-loved format, infuriating and invigorating viewers in almost equal measure.

''It's been a hectic, crazy, out-there, roller-coaster of a year,'' said Georgiadis, who presents the last show of the season on Saturday.

''My intention when I came in was to grab hold of this vehicle and really bring it to a whole new community, to make it more attractive to nought-to-30-year-olds while at the same time dealing with the challenge that the existing audience may not find me to their liking.''

A trained landscape architect, he became host after the acrimonious departure of horticulturalist Stephen Ryan, who had replaced long-running frontman Peter Cundall, the Manchester- born, Tasmanian-based gardener whose warmth and enthusiasm made him a favourite.

For traditional viewers, the change was traumatic. Georgiadis was criticised for his appearance (''I see Louie the Fly has a new job as host of Gardening Australia,'' one viewer wrote on the program's website), his apparent lack of specialist horticultural expertise and his focus on ''community and kids''.

But according to the ABC, the formula worked. ''Costa has delivered a freshness to the program and brought in a whole new generation,'' ABC's head of TV entertainment, Jennifer Collins, said. ''We still get the odd comment about his beard, but the audience has increased by 5 per cent this year to a series average of 630,000 [with a peak of 800,000 in July].''