I know Knock Out roses are low maintenance, but is there anything I should be doing to them during the growing season? I’m also getting holes in the leaves. Should I spray something?
Even thought they’re basically a low maintenance rose, there are always a few questions on taking care of them, like how often should they be fed, do they need to be deadheaded, and in some cases, what’s causing the small holes in the leaves? Knock Out roses are somewhat self deadheading, and you do not have to deadhead the spent flowers, but it does help to speed up the re-flowering process and increase flowers. You can see where the spent flower stems start to lose color and the new growth starts coming out below that. By clipping that spent flower (flower cluster) out earlier, we can speed up the process. Again, you don’t have to, but it does help. And if a branch grows faster than the rest of the plant, feel free to clip it back during the season to give the rose bush a more even look. When it comes to feeding, this rose gets by on light feedings, but for optimum re-growth and flowering, feed once every 4-6 weeks with a rose food (Espoma Rose Tone) – stop feeding around mid to late August. And as for these small holes in the leaves; they’re from a very hard to see leaf eating caterpillar like critter called ‘rose slug’. It’s not a slug, but actually a saw fly larvae. They’re lime green, look just like the veins on the leaves, and feed on the undersides of the foliage. Systemic insecticides (Bayer and Bonide) applied around the root system in mid spring helps to control rose slugs, as well as foliar sprays of insecticidal soaps or horticultural oils. Remember to spray the undersides of the leaves, rather than the tops. Now if you haven’t applied a systemic earlier, you still can, as there are multiple generations of the rose slug. And even if you did nothing at all, those Knock Out roses leaves will look bad, but they take the lickin’ and keep on tickin’ with colorful flowers, all season long – in most cases until late fall.