It is best to use a fertilizer that is classified as a slow-release type. Roses Roses will be completing their first major flowering period in early May. Spray modern rose varieties with fungicide on a weekly basis to control blackspot. Include Immunex fungicide in your spray rotation to extend control and give some residual. Mulch with pine straw to conserve moisture. When irrigating, apply water to the soil and eliminate wetting the foliage.
Wet foliage leads to more blackspot.
Remove old flowers to encourage the next flower cycle. This is becoming a more frequently asked question. Also, try to layer the landscape with plants that have varying heights - use dwarf and miniature varieties in the front. Plants selected for their vertical growth characteristics need to be in the back of a bed area. Louisiana Select Plants Louisiana Select is a plant promotion and recommendation program that is sponsored by the Louisiana Nursery and Landscape Association and the LSU AgCenter.