Back when I first started my garden, about 20 years ago, I planted Madame Isaac Pereire,the beautiful Bourbon. It grew well and flourished, but since then, none of the Bourbons I've tried seem to do well. Now, many, many things have changed in these years.By now, I have more roses than I can count-several hundred. I got cocky, and planted others too near the Madame,too. But the climate here has really, really changed for the worse; Italy has been very hard hit with global warming. Now, the summers have become unbearably hot and long-and DRY. So, I'm wondering if climate has something to do with my Bourbon problems. I looked up the Isles of Bourbon from whence these roses originate,wondering if perhaps they are sort of water-hogs by nature, but it wasn't too enlightening, since it seems like half of the island is dry, the other very rainy. I'd love to hear other rose gardeners' experiences with these roses,to help determine whether the problems here is just the climate,or if I'm doing something (improper soil preparation pops into mind) that is undermining my success with this type of rose. All comments welcome!

Here in SoCal, we grew Mme. Isaac Pereire back in the days when we sprayed religiously.

It mildewed, rusted, and taught me about blackspot. Honorine de Brabant was better, but not great -- same for Mme Ernst Calvat. So we declared Bourbons off limits.

Now, I'm growing "New Orleans Cemetery Rose" -- thought to be Pierre de St. Cyr -- a Bourbon. It's doing GREAT.

Which is all to say, I feel your pain and confusion.

I have a left and they are doing well. I planted Mme. Isaac Pereire in area that's no very good dirt. But I got blooms from it recently. Comte de Chambord is fabulous, not sure it's a Bourbon or Portland, it's getting so big, had lots of blooms from it.

It is confusing. When I say that for me they "struggle" what I mean is this: they all seem to have different"issues". Let's see now...
1) Modern cultivars like "Hommage a Soupert et Notting" , "Florence Ducher", and "Charles XII" all seem to grow pretty well as plants ,but have trouble flowering; they produce only bull-heads and proliferated, stunted blooms. Florence was a bit better last spring after I worked on the soil. Hommage was planted too deeply so a cane was starting to root; I dug it up and put it in a pot. Charles has been in a pot for a year, has grown a lot but not even one bud. Now, to be clear,I don't have good garden soil, and am still in the process of learning how to improve what I do have...but many other roses of other types seem to be able to be reasonably happy,so is it just that these Bourbons all happened to be unlucky, planted in worse conditions than these other non-Bourbons???
2) Mme Isaac Pereire #2 just doesn't grow. Zephirine Drouhin is a bit better, but gives the impression of "growing backwards"; i.e., the plants never seem to make real progress; they start looking a little better at one point, but after a few months seem to be right back where they started. Again,they same thing about the soil does apply,also I have so many roses and my garden is so big that I never manage to keep up with cultivating, fertilizing, etc.But other varieties seem to handle these conditions graciously...
Note that disease does not seem to be a particular issue.

ZD is a trouble one for me, I produced nothing, I gave it to my brother. To me, some plants take time to establish, but I'm very pleased with Mme. Isaac Pereire so far, it's better than Alchemist, that one gives me nothing yet.

How long did you have, ZD,So Cal? And how long have you been growing Mme Isaac Pereire? I've no experience with Alchemist myself; is that a Bourbon too?

I bought ZD last summer(2019) when it was on sale from J&P, I bought Mme. Isaac Pereire after that(Fall 2019). They are both planted in the same general area, very bad dirt. But I got at least 4-5 blooms from Mme. Isaac Pereire, and nothing from ZD.

Are they grafted or own-root?

I have no idea, Mme. Isaac Pereire is from Rogue, ZD is from J&P.

Just a grain of salt...
I try to avoid the criterion around classes...it can be misleading. The rose bushes themselves don't know anything about their identity, name family or provenance.... So my alternative way is to look at each individual as it makes progress or not. Sometimes as you say my bushes grow backwards, and eventually give up their ghost... However even then there's something extra to learn... I do grow Mme Isaac Pereire, which ought to be kind of a climber ( the sages at HMF say so). My specimen is own root and still behaves as a mid sized bush. I've got it 4 seasons ago. The first season it didn't do well so I lifted it and placed it in a grow bag under a more shaded position. It liked that and bloomed nicely still potted in its grow bag. This season, just in the leafing out stage, I will plant it again in ground in a mid shade situation. Perhaps it needs more root space under and the bag doesn't allow enough room for it to throw long canes. I provided a good general fertilizer two years in a row and it has doubled in size. When planting I will provide a very generous supply of organic matter. I use raw wool as mulch both in hole under the bush when planting and around the top of crown as a scarf. On top of the wool I add an inch of leaf mould and another of compost or horse manure. So if anything my roses are well fed! One variable less ... After these 4/5 years of growing roses my first bet will be always good garden soil. Like so many here at the RF I have a very poor soil ( sandy) to start with, that dries up in minutes after watering. So the second issue is how frequently can you water your roses. Water stress is a real problem in my yard. In comparison with my other HT's MIP is more water demanding. So that may be your second cause of low productivity.
All rose growers have been grappling with climate change worldwide... . At least for me, I can't change the climate ...( unless I grow my roses under cover which sometimes I do). So the alternative is figuring how to move along climate change trying to provide the conditions that suit best for each individual, by carefully watching how they are faring season after season. Yes, that may imply moving about roses. Some roses actually benefit from shade ( Clg Souvenir de la Malmaison or Mme Plantier). This I discovered by moving my potted bags around and found where each did best!
Like you, I've got nearly 400 bushes to deal with. Not all my bushes receive my TLC as they ought to in terms of my attention. Each bush has something to teach me all along. So when something goes below prime, then my attention starts to switch towards deepening my observation skills around it. Like any gardener anywhere, I still cope with vast ammounts of unanswered questions. Not always the right answer pops up quickly... most take years because:
each garden is unique as is each gardener

Arturo
PS I realized that I didn't mention one other factor: the aspect. My MIP is placed facing a west aspect. So it gets full sun all afternoon. It is cool in the morning under the projected shade of some scots pine. I also want to recall that I share the same climate pattern as bart does: mediterranean which means 0 rain during the long summer months, but temperature wise considerably cooler on the average to her place in Tuscany. I have to irrigate everything, otherwise no garden...just a desert!

Interesting, I planted Climb Souvenir de la Malmaison at the same area, pretty shady, very bad dirt, so crowded, and I got one or two blooms so far.

@SoCalGardenNut. If you are in a position to improve your soil ammending with compost/manure and liberally water it, your SdlM I expect it to don you with generous blooms.
Arturo

We did before we planted, but this is the worst area in my yard, I was storing junk here last few year.