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Top Questions About Knockout Rose Bushes

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Questions About Knockout Rose Bushes

  • Answered by
    MichiganDot on
    January 28, 2018
    A.

    Severe pruning in late summer, early to mid fall is a serious mistake. However, pruning roses shouldn't kill them, especially the hardy Knock-Outs. If you live in a region that has severe winters, I wonder if having them on a small berm is subjecting the crown and roots to killing temperatures. I wish I knew where you live and what happened exactly. Did they never leaf out after dormant season pruning? When you dug them out did you notice insect or grub activity in the canes or on the roots. Were the roots rotten and soft? I think I see landscape fabric. I suggest you remove it so each rose has a minimum of 4 ft of fabric-free access to water and nutrients. Despite how it is advertised, landscape fabric only lets some water and air through; on the slight hill you have, a lot of water will run off before soaking into the soil. And plant roots need oxygen; fabric restricts air penetration. And it doesn't prevent weeds anyway, as many of us have discovered. I would not plant until I was sure what happened to the plants that died. If you wish to add further information, we'll see if we can provide further help.

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  • Answered by
    MichiganDot on
    February 10, 2018
    A.

    Usually this discoloration is meaningless; however, do watch for problematic rose black spot. When you do spring pruning, carefully examine the pith or center of cuttings. It should be a whitish color. There should also be a visible green ring just beneath the outside. If the pith is tan or darker and there is no green ring, recut the cane further down. I live in the north and some die-back is expected when winters are colder than normal. If you fertilized or pruned too late last year, your plant is likely to suffer die-back since it didn't have time to harden-off new growth. New growth needs about 6 weeks before frost to prepare for winter.

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  • Answered by
    MichiganDot on
    February 14, 2018
    A.

    I don't know that you can blame the mulch. This viral infection is hitting the entire country. If you have any multiflora rose near you, remove it as it is the main host plant for the disease. This website discusses containment/treatment; most just recommend removal, including plant roots. good luck. http://www.missouribotanicalgarden.org/gardens-gardening/your-garden/help-for-the-home-gardener/advice-tips-resources/pests-and-problems/diseases/viruses/rose-rosette.aspx

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  • Answered by
    MichiganDot on
    February 24, 2018
    A.

    If they have sun until 3 pm that's fine. No morning sun but full afternoon sun is fine as well. Aim for at least 6 hours of direct, full-on sunlight. In addition to giving you more blooms in full sun, sunlight helps ward off foliar disease and increase plant vigor. By definition, full sun is over 6 hours daily. More is better.

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  • Answered by
    MichiganDot on
    March 1, 2018
    A.

    I think determining resistant varieties is still in progress. However, I did find a comprehensive article on rose rosette virus. Page 7 discusses *reported* resistant varieties. http://www.newenglandgrows.org/pdfs/ho_WindhamRoseRosette.pdf

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  • Answered by
    MichiganDot on
    March 11, 2018
    A.

    Here is a good rundown on rose pests. http://www.missouribotanicalgarden.org/Portals/0/Gardening/Gardening%20Help/Visual%20Guides/Rose%20Problems.pdf. You may have scale insects which over-wintered on your canes. Here are some treatment options: http://www.clemson.edu/extension/hgic/pests/plant_pests/flowers/hgic2107.html

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  • Answered by
    roseman on
    April 8, 2018
    A.

    It is more likely that they got damaged back at the cane somehow or spider mites have gotten to them. Look for spider like webbing in and about the foliage. If found, that is likely spider mites. For spider mites be sure you use a miticide to control them, using regular insecticides will only kill off their natural enemies and the spider mite population will increase.

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