The National Dahlia Society vice chairman said at the Plants for the Future plant breeders event that breeders should not try and "spend huge amounts of time, money and resources re-inventing the wheel" and that there were 35 RHS award of garden merit dahlias "sitting out there. Take your pick - they are fish in a barrel."
Gillam said lilliput dahlias should replace garden mums, which he said were imported and have short shelf lives.
Gillam, who is now buying bulbs for for Choice Marketing, said "we over-estimate the horticultural knowledge out there", adding: "The masses are the ones who walk in the garden centre, not knowing what they want to buy".
He said specialists such as Halls of Heddon were the only outlets for many dahlias and that 'Bishop of Llandaff' should not be the only variety out there.