My mini roses are on my porch. The leaves are turning yellow and getting black spots on them. why?

Question

They are still blooming and there are big gaps between the leaves, but some of the leaves are turning yellow with the black spots. Can anyone tell me what is wrong with my roses? I would greatly appreciate it.

Answer 1

The disease they have is called...you guessed it..."blackspot." It's a fungal disease that is very common on modern hybrid roses such as the minis you have. Preventative measures include: not watering the rose from above and increasing air movement by not spacing plants close together.

What you can do now is to cut off (and throw away or burn) any affected leaves. Do not let them lay in the soil around the plant as blackspot spores can persist there for a longtime. A fungicide that is reccomended for use on roses (read the label carefully) can help if the blackspot is severe.

BTW blackspot spores usually only germinate in temps below about 75 degrees F, so you can go a long way in reducing this disease by limiting evening moisture in summertime...wetness coupled with cool nighttime conditions spreads the disease.