Grandiflora is a category that was essentially invented by the American rose establishment to accommodate one rose: the ever-popular Queen Elizabeth. Ostensibly, the category combines the best traits of HTs and Floribundas, but it has become a very muddy classification. If they had it to do over again, I suspect that those who are/were in charge would have classified QE as an HT and moved on. Grandiflora is a category that simply doesn't exist in most parts of the rose-growing world.

A grandiflora is a rose that has hybrid tea type blooms but blooms mostly in clusters or sprays like a floribunda.

And they should be treated just like you would treat a hybrid tea. If hybrid teas are disease prone in your area, grandifloras will be too. And not all grandifloras bloom in clusters all of the time just as not all hybrid teas grow one to a stem all of the time.

I think the only grandifloras I grow are Gold Medal, Queen Elizabeth, Honey Dijon & Lagerfeld. In my garden the rose that performs most like a grandiflora (but isn't one) is the HT Crystalline.

Been growing roses for years....care for over 3000 plants....grow every kind you can think of and still have no clue what distinguishes a grandiflora from many Hybrid Teas and some Floribundas. My Moonstone sends up huge sprays, much more so than my Gold Medal....yet it's a HT and Gold Medal a grandi... Crystalline is a spray machine, yet a HT. I'm not sure what the criteria is.....so I just treat them all as HT's and leave it at that.
Michael

I would take a more pragmatic approach to this question and say that a Grandiflora is any rose which is declared to be a Grandiflora by the International Cultivar Registration Authority (ICRA), which operates under the auspices of the American Rose Society. I assume that the ICRA uses some of the guidelines suggested in the above postings but I suspect that almost every rose now classified as Hybrid Tea or Grandiflora could be given the opposite classification without seriously violating the guidelines, and I also suspect that the classification suggested by the breeder in his initial application for registration is likely to be honored so long as it does not obviously violate the guidelines. In other words, if the breeder says it's a Grandiflora, a Grandiflora it will be.

Here is a link that might be useful: ICRA Application

I think that the Grandiflora class has become so muddied it is about useless. I see many so-called HT's that to my way of thinking bloom like what I think a grandiflora should be like-- flowers of hybrid tea form that bloom mostly in sprays of 3 or more roses per spray. It seems that some breeders don't want to use the category as they think it is sudden death on the open market to call a newly developed rose cultivar a grandiflora instead of a hybrid tea. I just think a little honesty, education, and common sense are in order on this matter.
Personally I love it when I see a rose I consider a grandiflora as I really like how they work in my vases in the house.
Just my two cents......
John

Thank you all for your insight.

So do you prune them like a Tea or a Florabunda?

Pat Tea, That's an impossible question to answer because different varieties have their own distinct preferences when it comes to pruning. Some HTs greatly resent being pruned too low, others go on about their business regardless of how you might lop them off. The same can be said for Floribundas and Grandifloras. In my experience, you just have to learn by trial and error.

I've aleays pruned my grandifloras the same as my hybrid teas.

Why was Sheila's Perfume a floribunda? Why was it not a grandiflora or a hybrid tea? And why was Cherry Parfait a grandiflora instead of a floribunda?

Patricia, Those two varieties underscore the arbitrary nature of the classification 'system'. Its hybrizer (Meilland) introduced Cherry Parfait as a floribunda (or 'cluster-flowered' variety), and the rose carries that classification throughout Europe. When it arrived in the US it was renamed and proclaimed a grandiflora.

As for Sheila's Perfume -- well, who knows the rationale behind that one? It's classified everywhere as a floribunda (CLUSTER-flowered in its native Britain). If anyone has a photograph of a typical floribunda spray of Sheila's Perfume, please post it.