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My Knockout Roses are not doing well; need advice!


By Lisann

Maryland, United States Us

Last summer I put in two Knockout Rose bushes. I have prepped the soil (all clay) by digging down about 20 inches and backfilling with sand, rocks and humus/manure to make sure they would not be too wet. I even mounded them up a bit but with the heavier rains this spring, I believe they are too wet. They seem to have "rust" spots, they are quite spindly and pale colored. Also, the stems are blackened in some spots. They did bloom but, after the last heavy rain, they have not bloomed again. I also had a lot of trouble with caterpillars and mites in late May. I have trimmed them down and fed them but I am not sure what else to do for them. They get sun all day (East-West) esposure. They are surrounded by rock pavers but I heavily mulch them to provide enough acid. In the picture they are near the top left, in front of the day lillies.




removed question as i just noticed where you are, sorry.

18 Jun, 2009


I assume you know that these roses grow well in your part of the world and that's why you bought them.
That said, roses here are very happy to grow in clay soil, do not require acid soil, but do get diseases, as yours might have done. You could try spraying them with a combined fungicide/pesticide, give them some specialist rose food, but, from reading your info, it does sound as though you might be killing them with kindness! I can't see any reason why the roses you've bought should require acidity, nor be unable to thrive in a clay soil.

19 Jun, 2009


I am wondering what you mean by rocks? Also, the mounding up you refer to. There isn't soil or mulch going up the main stem is there. This would stress the plant. Also, as Bamboo says, roses do not require an acid soil to grow and do very well in clay soil. Perhaps they are just too wet?

19 Jun, 2009


Thanks to you both for your replies. I may be killing them with kindness AND being helped along by Mother Nature! We have had a horribly wet spring here and even my moss has drowned between the pavers in the back. I am keeping my fingers crossed for dry weather and hoping they will make a come-back. Then I will try to address any diseases I can identify.

19 Jun, 2009


Hi Lisann. We had two very wet summers in 2007, and 2008 and my roses suffered terribly from blackspot. I try to garden organically, and don't use any chemical sprays. Planting alliums and chives near, or under your roses may help....

19 Jun, 2009


What about the heat on knock-out roses

15 Jul, 2012


Goodness, Frenzy, you managed to find a pretty old question, lol!
I saw your post today on your roses - I believe you're experiencing unusual heat in your part of the world, and I think your question was whether you just watered, or soaked. I'd say soak, and by that I mean the ground around them, its always better to give them a really good soak less often than a bit of water every day. Best done in the evening, after the sun has gone. As your heat is so intense,until it eases off, you may need to soak every 2 or 3 days because your plants are new this year.

15 Jul, 2012

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