Question

In celebration of our 50th wedding anniversary-2007, we planted Knockout roses hoping for some color and not too much trouble.>Houston TX ,plants in  a bed on the front/north side of our home,
half day+-shade in winter and springand sunny ,hot and humid in summer.Begonias love it all year long!
The pruned bushes are putting out healthy new leaves but the plants are also covered w/ older leaves turning that are yellow w/ lots of black spots.What do I do now? Thanks.

Answer
Knock Out roes have been well hyped, both by rose nurseries and by gardeners who planted them. That said they are still only shrub roses and because they are roses, they are prone to the same problems as any other rose. Although they are supposed to have good disease resistance, I have got many questions concerning disease problems with Knock Outs. Most roses require hours of full sun per day. They also really don't like humid conditions because it is ideal for any fungal diseases to grow in and from your description, the roses have got Black Spot. Any rose fungicide( and there are many brand name ones) sprayed by the instructions on the label, will keep the fungal condition under control. Because Black Spot spores float around in the air, it is not possible to totally cure it. Pick off the dead or yellow leaves before spraying and burn or put them in the garbage as they will be filled with Black Spot spores. I am sorry that your roses are not doing well as Knock Out is one of the better roses.