What causes black edges on rose petals?

Answer 1

There are a number of diseases that cause sunken, black, "mushy" lesions on rose leaves, primarily "black spot" which is a fungal disease. Control of fungal diseases on roses depends on the management of water. Avoid overhead watering, or watering in the evening, which allows water to stand on the leaves overnight. Black margins on the rose petals can also be a fungal disease, but is more likely the result of physical damage to the tissue, since the flower petals are dead, and don't often act as host to pathogens. Look for earwigs or other insects that feed on flower petals. If they have chewed the edge of the petal, it could turn black as it decays. For a definitive answer, bring a sample to your local agricultural extension agent. Be sure to call first so that the sample will be fresh when it is examined.

Answer 2

Black edges on rose petals can be caused by a fungal disease called black spot, which is common in roses. This disease thrives in warm and humid conditions, such as after rain or high humidity. To prevent black spot, make sure to provide good air circulation around the plants and avoid overhead watering.