The annual event, which has been running since 2006, raises money for Greenfingers and attracts 250 garden journalists.
This year it moves from RHS Lawrence Hall to the Barbican because the halls have been sold to Westminster School.
Organisers says the new venue offers better access for build up and breakdown, and on-site parking for exhibitors and guests. Some 73 exhibitora are booked, while 80 showed in 2012. Some space remains available.
The exhibitor list includes a wide range of garden product suppliers including Agralan, Carbon Gold, Solus, Neudorff, Kubota, Roundup and Scotts Miracle Gro.
Also exhibiting will be horticultural collegs, trade associations and garden attractions Batsford Arboretum and Waterperry Gardens.
Plant suppliers include Claire Austin Hardy Plants, Crocus, and David Austin Roses.