Hello,
I have a few year old knockout rose bush that is about five and a half feet tall planted in my landscaping. Recently, I noticed that some of the leaves on it, especially the lower leaves, had started turning yellow, and a few have fallen off. I check on the plant about every 2-3 days, to check for any potential problems and also to check the moister level. The leaves started to yellow virtually overnight, having started turning yellow and dropping within the past few days.
After doing some research on it, I believe the issue to be heat and water related. I am in central Texas and it has been nearly 100 degrees each day for about one and a half months. When researching I found that the knockout rose can lose some of its leaves in temperatures above 85 degrees. We have also had some quite heavy rains lately in the last few months, which might also be contributing. Other causes of yellowing and dropping leaves that I have found were nutrient deficiencies, including iron and nitrogen deficiency, bugs such as spider mites and aphids, fungus infections such as rust, black spot and powdery mildew, and lack of sunlight or drought. I don’t believe that it is a nutrient deficiency, since I fertilize it every 4 weeks with Garrett Juice. I also don’t believe it to be any pests, because there are visibly no aphids or spider mites on the plant, and also I am spraying the plant with neem oil, which I started doing to try to get rid of grasshoppers, but that’s for an unrelated issue. I similarly don’t believe it to be rust or mildew, since it doesn’t appear to have any rust or mildew on it, and I also don’t think that it is rust or mildew because of the neem oil that I am using, which is supposed to protect against fungal infections. However, I am unsure if the issue is because of black spot. The rose also gets adequate sunlight daily, and we don’t have a drought.
I would like to know if there are any other possible causes that could be the source of this issue, and also how to fix those problems. Also, is the yellowing and dropping leaves anything to be concerned about, or is it just something natural and to be expected? And also, does the plant look as though it will survive it? I am just an amateur gardener and would like some more expert opinions on it, and any feedback would be appreciated.
Thank you,
-Nathan
