I've had this for 2 years and it has only bloomed once in the spring. Does this one need some size before it will perform? It does not seem to appreciate the heat of summer and looses about half its leaves, but continues to put out growth - just no flowers. I agree it is pretty disease resistant, but it will definitely spot when conditions favor it. I've also had a bit of mildew here and there. The plant does seem to shrug this off. You can prune back the affected areas and that is usually all it takes - or the plant will just drop the affected leaves and grow new ones. Just wiish it would bloom.

1756 – 1791 Wolfgang-Amadeus compositeur autrichien

I wouldn't call this rose (very) disease-resistant, for it gets some Blackspot.
And Mildew at a dry spot or after a longer dry period.

Looking at the Lineage info (the parentage tree) of Mozart, I found out that at the "Rose Seedling of Mrs. W. J. Grant the same photo's are uploaded as for the rose "Mrs.W. J. Grant" itself.
is that a mistake, or are there no pictures of this seedling?