Ask Heirloom Gardener: What Should I Do About Black Spot on my Roses?

Question from the mailbag (heirloomgardener [at] aol [dot] com): I have about 30 rose bushes and most are struggling due to black spot. What should I do?

Answer from Heirloom Gardener: Regarding the black spot, I wouldn't worry about it at this time of year. It won't kill the plant, even if all of the leaves fall off. If you want to prevent black spot on your roses next season, start your maintenance in the spring. I spray dormant oil right before the plant leafs out which kills any over-wintering spores that cause black spot as well as insects, etc. If you spray it now, it will kill the plant. After the plant leafs out, I spray with neem oil that smothers the spores every two weeks except during the heat of summer when it will burn the leaves.

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