Eight gardening celebrities, including Titchmarsh, Christine Walkden and Toby Buckland are setting questions and then recording them on a CD which garden centres can play on the night.
BBC Gardeners World Magazine is getting involved too, by providing the pictorial round.
Sue Allen, one of the organisers of Garden Re-Leaf day says she hopes that centres will invite their gardening club members, customers and local horticultural societies to what is hoped will be the biggest concurrent gardening quiz ever.
Garden centres are asked to donate £50 for the fundraising pack which includes the CD quiz, full instructions on how to run the evening, press releases, a pdf poster and a cd of Greenfingers images and gardens. The GCA office is co-ordinating the quiz and all centres, not just GCA members can take part.
Alan Titchmarsh will also announce plans for the inaugural Garden Re-Leaf Day at the Garden Media Guild Awards. The day is garden centres' effort to emulate Comic Relief's Red Nose Day.