We have Walter Lammerts to thank for the Grandifloras. He created a rose type that didn’t quite fit into existing groups. They were similar to Hybrid Teas, in that they had that typical high center, and large showy blooms.
Yet they also inherited the Floribuba trait of blooming in sprays rather than on single stems.
And to top it off, they would grow taller than either of these, 6-8′ was not uncommon.
The first of these was the “Queen Elizabeth” which is still popular more than 60 years later.
So, what exactly is a Grandiflora? If we look at the name we would assume it means something along the lines of “Big Flowers”. But perhaps it would be slightly more accurate to say “Lots of flowers”, as that is one way to distinguish a Grandiflora from a Hybrid Tea rose.