Cape Diamond . . . Guarantee of Black Spot Resistance?

A new introduction, Cape Diamond, was brought to my attention over the weekend at our local rose society meeting. The Weeks website and their catalogs are stating “free of black spot, powdery mildew, rust & downy mildew . . . guaranteed”. Does anyone have any experience with this rose? Is it really as good as it states? With all of the strains of blackspot, etc. can they really “guarantee” resistance? And, for how long?



I am cautiously optimistic about this rose and look forward to growing it. KNowing it’s parents are ‘Marie Victorin’ and ‘Louis Jolliet’, I wonder if cercopsora leafspot will overtake this rose as it does its parents (and L83) and like you said Andy, if the likely race specific resistance will be broken down. ‘George Vancouver’ is another L83 seedling, like both of CD’s parents, and there is a race specific resistance gene in it that has broken down in the midwest and Vance Whitaker for part of his Ph.D. is characterizing that resistance gene from GV and reported on it at the American Society for Horticultural Science meetings last summer. It doesn’t seem there is much underlying horizontal resistance in GV after this one resistance allele is compromized unfortunately. I suspect CD is relatively hardy at from the parents (MV dies to the soil usually here and LJ is hardier).



I’ve had my order for this one in for a few weeks now. It’s likely the only rose I’ll actually buy this year. I primarily want it to marry with my remontant glauca x pendulina and kordesii hybrids.

It is nice that there is some yellow in it’s pedigree.


With so much pink in its background I would expect that escaping the pink is going to be a task and a half, but as Robert said, at least it has Arthur Bell in its pedigree…

I’d cross it with a Rosa wich. groundcover, personally. The pink lineage does seem like an uphill battle…

That look like a niffty rose.

I would like to cross that with my kordesii X basye amphi seedling–

I don’t mind of pink roses at all. I’m looking for a way to bring remotancy to my seedling but keeping in line with kordesii.

I acquired this rose bare root from Edmunds Fall 2008.

I thought it sounded promising. Since it was newly acquired I used it strictly for pollen last season.

Long story short, it is pollen fertile with most seed parents I tried it with.

Unfortunately the majority of descendants seem prone to Powdery Mildew.

I’m getting ready to cull two of the crosses I created. I’m offering them here in case anyone wants to try to carry them forward. There are several seedlings of each cross.

They should probably gain size before they go anywhere, assuming anyone wants to play with them.

They should be fairly cold hardy.

  1. (Country Dancer x R. kordesii)X Cape Diamond

  2. (Country Dancer x (R. glauca x R. pendulina) X Cape Diamond

I ask to be reimbursed for postage unless I owe someone a trade.

Feel free to discuss any thoughts. First come first served.

Contact me privately. Robert


I planted Cape Diamond last year. At this time I still can’t attest to its winter hardiness (although I expect it to be quite hardy). While it only has one summer under its belt, I can tell you that it was one of the healthiest plants in garden and displayed no disease whatsoever even though all the usual disease organisms were present (mildew, rust, Downey mildew, blackspot, and the spot diseases). One can always be disappointed as time goes on but I consider it promising. It is good to hear that it is at least pollen fertile.


It set seed at all the local nurseries. It made a lot of small to medium sized orange hips.

‘Cape Diamond’ it’s self does not mildew here. It repeats but not heavily. I never assume repeat isn’t better in other climates.

This year I will try it for seed.

There are a few crosses still hanging in there so far for mildew resistance. Again there is hope.

Seedlings are spoken for now. Thanks, Robert

Something like Cape Diamond x Oso Easy Peachy Cream sounds nice. Cape Diamond is too boring for me to use space on, but that is what I would attempt. I think Cape Diamond has potential, but from what I could see, it has some issues in being a great landscape plant. The rebloom is slow and the space between the plant and blooms is too …spacious. It needs to be more compact and everblooming to serve a landscape well. It seems like it is one generation off from being the excellent landscape plant it could be.

I would never think of using this cultivar in a breeding program. The shrub has very poor architecture. It shouldn’t have been introduced, since there is nothing special about it.

Paul, I feel very much the same way about ‘Home Run’. I don’t like its architecture at all.

‘Home Run’ does have poor architecture, but it’s descendants can be much better.

I bought Home Run a year ago and it was totally eaten alive by Black Spot. If it happens this year it’s gone. I don’t like the architecture either. I may get rid of it for that reason alone.

lol Home Run looks like Stick-ette. The architecture reminds me of that one teacher anyone has had that says as s/he is at the board, “Now kids, I cant draw, but here is a stick figure.” I’m guessing that was inherited mainly from City of San Fransisco since In the Mood shares the same hideous fate.

Despite Home Run’s flaws, it has a lot of amazing benefits. One of the things I liked about both Cape Diamond and Home Run is that they didnt seem to be bothered much with the summer heat here. Usually the roses at nurseries look awful after July, but they looked just as good/boring as they did in the spring, lol.

Jadae said,

“Cape Diamond and Home Run is that they didnt seem to be bothered much with the summer heat”

This is true. They do have better heat tolerance than most.

It’s also true the growth habit of both leaves much to be desired.

‘Cape Diamond’ is 50% “L83”, It’s heavily line bred on kordesii.

Unfortunately all that hardy species influence doesn’t translate to desirable garden architecture in this case.

Apparently it’s really hard to get all the qualities we look for in a healthy hardy garden Shrub rose.

Have you ever seen L83, Robert? Its not hard to see where the awkward plant architecture comes from. And yet, my own work has shown me that L83 can breed plants with some grace of form.

“L83 can breed plants with some grace of form”

Obviously the potential is there. There are those with far more resources than we have working on the problem.

No doubt there are dozens of others in the pipe line. We just haven’t seen them yet.

Till then, in this case, it looks like they threw us a bone, for now.