Buckland said: "There's a rumble in the press about the demise of the gardening clubs but we have 1,000 people from gardening clubs booked already and we're getting three more clubs a week so we could have 1,500-2,000 people pre-booked for the festival.
"Nurseries, including mine, have had a horrible winter and to know something is around the corner and we have plant-hungry buyers from garden clubs who are gold dust in gardening terms, shows to nurseries we are working really hard to make sure people who buy plants will be there."
The event has 100 stands and all talks are free to enter. Charlie Dimmock and Cleve West are headline speakers.
Buckland is also hosting a garden festival at Powderham Castle, near Exeter in Devon on April 29-30 April, featuring Joe Swift and Christine Walkden.