''We are hoping for a big turnout, and the public are very welcome,'' Mr Wardell said.
The first day will be a half day, starting at 1pm; both Friday and Saturday will be 7.30am starts and will go all day.
Mr Wardell said it would be entry on the day but he expected competitors to come Otago and Marlborough.
He said the club was in good heart.
''We're a typical small country club with a hard core who do the work when events are on.''
The club is no stranger to big events.
It has hosted six Canterbury championships - 1924, 1958, 1968, 1978, 1987 and 1994 - and the New Zealand championships in 2014.
Mr Wardell said the venue was rated as one of the better grounds in Canterbury, and the club was very grateful for the long-time support of former station owner, the late Archie Reid.
The club was formed after a gathering of interested people in Geraldine's Crown Hotel in August, 1920.
The first trials were held on the Blair Bros property at Peel Forest, with a five shillings entry fee. The trial, records show, was run in beautiful weather.
Competitors came from as far as Mt Somers, Kimbell and Kurow.
In 1924 the Geraldine club ran the first Canterbury championships, with sheep from Mt Peel Station.
There were 17 huntaway entries and 27 heading entries.
But as successful as the club is, there have been hard times: early in the Depression the club went into recess but got back on track in 1935, until world war intervened.
But the club provided funds from trials and concerts to patriotic and soldiers' funds.
In 1941 a committee of women was formed to oversee trial catering, and in 1956 the trials moved to the Ritchie and Evans' properties, with sheep brought over from Blue Mountain Station, owned, then, by Nix Buick.
At times, the sheep had to cross swollen rivers.
The trials shifted to the steepish Reid property in the Waihi gorge in 1974 and have stayed there.
In 1969 the club employed its first female secretary, one of the first clubs to do so.
There have been five female secretaries, and the Geraldine club also had the first female president, Dinah Osbourne.
The 100th event will feature the long pull, short head and yard, zig zag hunt, and straight hunt.
Waihi Gorge station will supply the sheep.
-By John Keast
Central Rural Life