1. Problem With Knockout Roses

Asked by blackthumb - June 6, 2011

Why do my Knockout Roses have holes and greyish white spots on many leaves? Also, now they are starting to sprout some red leaves. . . is that normal?

  • It is hard to say without actually seeing a picture. The holes could be insect damage and the greyish white spots could be the insects if they move. Otherwise it may be a bit of a fungus infection. Spraying with an insecticide of your choice should take care of the insect damage. Be sure to spray up under the foliage too as some insects like to hide underneath the leaves and thus dodge the insect sprays while they continue to do damage. The red to maroon colored leaves are new growth. They will turn green as they mature. Along with that new growth will come more buds for more blooms! That is a good thing indeed!! Oh yes, for the greyish white spots if it is a fungus of some sort, spray the rosebushes down with a fungicide. My favorite and earth friendly fungicide is called Green Cure. It is available on line and at some garden centers and nurseries.

2. Grey Spots and Holes on Knockout Rose Bushes

Asked by Anonymous - June 6, 2011

Our knockout rose bushes have greyish spots on the leaves, which seem to eat a hole in the leaf right where the spot is. Our bushes are covered with them. We have looked carefully and it is not an aphid or any kind plant pest. Can you tell me what this is and how to get rid of it?

  • At first, I thought you might have powdery mildew. However, the powdery mildew typically does not make holes in the foliage. Some worms and caterpillars, on the other hand, come out at night to do feast on plants, so it still could be a pest of some sort that you just are not able to see due to the timing of the attacks. I would recommend spraying the bushes down with some Ortho Bug B Gon or similar insecticide.

    Sometimes water droplets get on the leaves from sprinkling systems or even a mild rain. Then the sun comes out hot and intense and the droplets act like little magnifying glasses on the foliage, causing burn spots that then turn into holes where the leaf has been burned. This can happen with the application of some water soluble fertilizers and other sprays that are applied at the wrong time of day.

3. Watering Knockout Roses

Asked by Anonymous - June 6, 2011

How frequently should Knockout Roses be watered?


4. Knockout Rose Diseases

Asked by Anonymous - June 9, 2011

Planted 5 knockouts last spring and they did great. This spring they bloomed and were beautiful. Then, about a month ago, I noticed one plant beginning to have wilted leaves. The leaves began to turn yellow, fall off, and the rose bush died. Now, 2 more are doing the same thing. That’s 3 out of 5. One bush looks healthy, has started re-blooming. And last but not least, the 5th bush, although re-blooming, now has very few leaves. Can you give me any ideas as to what may be happening. I have seen signs of voles in my yard for the first time and my neighbor says they are the culprit, but I cannot find any signs in or around the rose bed.


5. How to Maintain Yellow Knock Roses

Asked by Anonymous - June 13, 2011

What do you do to get your Yellow Knock Out roses to maintain their yellow color? When they are in the bud stage, they are yellow; but when they are in full bloom, they turn white.

  • Unfortunately this happens with most yellow roses when the weather gets hotter. In the cooler spring temps and early fall temps the yellow color is typically richer and lasts longer. You can also add some extra potassium to the soils as it will help build the root system and enhance the color in roses and other flowers. If you have never given your roses Kelp Meal, that is another thing you can give them that helps them fight stresses and disease, along with providing some great nutrients. The stronger the rosebush is, the brighter the bloom color and overal vigor of the rosebush.

Read more about Knockout Rose Bushes

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