Blom designed the Chelsea Flower Show Healing Garden with the Prince of Wales in 2002. She was unwilling to comment, as was B&Q.
Blom has always used Crocus to supply plants for Chelsea in the past but is believed to have chosen Hortus Loci this year.
Adam Frost is designing for Homebase, and Roger Platts is believed to be designing show sponsor M&G's garden.
Chris Beardshaw, James Wong and Michael Balston are designing for unnamed clients. Nigel Dunnett is designing for RBC.
Christopher Bradley-Hole is designing the Telegraph garden, while Ulf Nordjfell is designing for Laurent Perrier.
Hillier has linked with Beazley again. Diarmuid Gavin applied late but is set to return.
The Sun will stage four Scotts Miracle Gro'ers displays with plants and crops grown by schools. See www.lovethegarden.com/schools.
Other gardens are to be announced in late Novem-ber. The RHS said it is keen to stop any more names of designers being released before then.
The 2013 RHS Chelsea Flower Show runs from 21-25 May 2013.