For black spot I use Serenade.
I buy the 2.5 gallon jugs.
I apply as often as I fertilize on average, some time more often especially in humid weather but I apply liberally in fall and spring.
It doe not eradicate black spot but controls it greatly.
Bayer, which now manufactures Serenade under license also produces Sonata, similar item different bug, and one gardening site recommended altering between the two each year so the bad bugs do not adapt to one type.
For ground cover I use cocoa been hulls to about two inches. They lose their color and get a semi-hard crust but underneath they stay moist and keep the ground moist.
Up here, if I put a mat over the roses before I apply leaves in fall so they do not get scooped up in spring, they will last two years with minimal touch up before they decompose to the point they need a redo.
Addendum:
Large roses; Until I started to bury I though a large HT rose was one the got over two feet high, now, one, is taller than I am and I am six feet tall.
Its large canes are bigger around than a mans thumb and the side canes are as big around as a man's little finger.
It is either normal for the variety or this is an oddball as it is not bushy in any form but more like huge sticks with flowers and leaves on the end of each stick.
It has become a problem with how to bury as it is also broad. The branches, and they are branches not canes, are amazingly flexible but it now takes a hole over six feet long and two feet wide to bury.
For once I am glad I have heavy clumping soil as I take big chunks, 12 x 6 of soil and set them on the branches to keep them down and compressed.
If it were a red rose I would be very happy but it is pink, ughh, but it has large blooms .
At this point, depending on money, I intend to redo the rose garden, add and relocate and I will see if I cannot get a picture of Frankenstein when it is in all its glory.
Not giving the South garden the attention it used to get is really starting to take its toll, so this year some thing has to be done and not just with the roses.
