All right, I've finished my highly unscientific study of black spot. I have to say right away that I do nothing to control it and my gardening practices are almost calculated to cause it. I plant everything close together, water from overhead unless the plants are too tall, and I never pull off the damaged leaves and discard them properly.
Consequently, any rose that doesn't get black spot in my garden is one heck of a performer. I conducted my test with the most rigorous criteria, disqualifying any rose that had even one affected leaf.
I think the results are shocking. Out of more than 1350 different cultivars, only 24 roses were completely free of black spot.
I can only make a few generalizations, largely because of the unscientific nature of this test, but the Bourbons, hybrid perpetuals, and hybrid musks were total duds in the context of BS resistance. The gallicas and moss roses were almost BS-free, but only one of them made the list -- Cardinal Richelieu -- and even that one unfortunately has no pest resistance, so it's by no means the perfect rose. Some of the teas and chinas looked okay and some looked awful.
As far as hybridizers go, the Austins had good resistance, but only 2 of more than a hundred Austins in my garden had no black spot whatsoever. Two of the roses on my list are from the Kordes Fairy Tale series and there are a couple of other Kordes roses there. The Meilland roses looked fairly good, but only a couple made the list. The hybridizer with the very best-looking rose foliage in my garden today was J.B. Williams. Carruth roses also seem to be standouts. The Bucks are not resistant. I have more than a hundred Buck roses and they all have black spot this week.
Only 3 of the 24 on the list are own-root roses. The rest are grafted, about half on Multiflora and half on Dr. Huey.
So, here is my list of roses that don't get black spot in my garden, although they might get it elsewhere.
Cardinal Richelieu, Carefree Delight, Carefree Spirit, Chicago Peace, Colette, Delany Sisters, Festival Fanfare, Gebrueder Grimm, Gertrude Jekyll, Helen Hayes, Jacob's Robe, Judy Garland, Macho Man, Marie Curie, Permanent Wave, Pomponella, Rosenstadt Freising, Royal Bonica, Sisters at Heart, Sunstruck, Super Dorothy, Sutter's Gold, The Charlatan, and The Prince.
It's highly possible, I suppose, that some of these 24 might come down with black spot next week or the week after, but for now they look perfect, especially in comparison with the roses surrounding them.
