Co-director Mark Fane said: "Christopher and I last worked at Chelsea together in 1997 when he created the Latin Garden, again for the Telegraph, which won best in show. Many viewed it as a 'game changer' for Chelsea garden designs."
Meanwhile, Hortus Loci is set to supply three show gardens. Director Mark Straver said: "Four last year nearly killed us. Three is enough to deliver economies of scale growing plants in groups. We're not scoring points - we scored enough last year."
He said he did not want to "jump the gun" on the RHS launching Chelsea at an event at show sponsor M&G in London in late November.
The RHS said they were keen to stop names leaking out and would talk to Crocus about releasing their designers on its blog.
Michael Balston, Jinny Blom, James Wong and Diarmuid Gavin are likely main avenue designers for the centenary show on 21-25 May.