Q&A for How to Prune Knockout Roses

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  • Question
    Why are my knockout rose bushes just skinny and spindly now after blooming for about 6 years?
    Lauren Kurtz
    Professional Gardener
    Lauren Kurtz is a Naturalist and Horticultural Specialist. Lauren has worked for Aurora, Colorado managing the Water-Wise Garden at Aurora Municipal Center for the Water Conservation Department. She earned a BA in Environmental and Sustainability Studies from Western Michigan University in 2014.
    Professional Gardener
    Expert Answer
    Prune your rose bush to about 6”-8” above the ground. This is called a rejuvenation prune and will encourage bushier growth.
  • Question
    How can I prune my roses to a 3-foot height?
    Lauren Kurtz
    Professional Gardener
    Lauren Kurtz is a Naturalist and Horticultural Specialist. Lauren has worked for Aurora, Colorado managing the Water-Wise Garden at Aurora Municipal Center for the Water Conservation Department. She earned a BA in Environmental and Sustainability Studies from Western Michigan University in 2014.
    Professional Gardener
    Expert Answer
    Prune them in the spring before the leaves appear. Prune to the desired height. Prune above an outward facing bud and make a 45° angle cut.
  • Question
    My roses were trimmed too late in the spring and only bloomed once. I want to cut them back now due to their weight and what looks like an insect problem. How should I do that?
    Community Answer
    Leave three main branches about twelve inches tall. You'll be surprised how much regrowth and blooms you get.
  • Question
    Can a knocker rose bush be transplanted to another location?
    Community Answer
    Yes, it can.
  • Question
    If my knockout roses quit blooming and have white spots on the leaves after I pruned heavy, will they survive?
    Community Answer
    The white spots are either fungal or mites. Find your local gardening place and buy a good spray to help ensure survival; taking a small sample with you helps. Also, don't prune too heavily in the growing season.
  • Question
    How do I know when to prune my bushes?
    Community Answer
    Start pruning if the leaves are getting green or are too long for you.
  • Question
    Should old, dead roses be cut off?
    Community Answer
    Yeah. It can hurt the rest of the rose, and it's useless and ugly.
  • Question
    Should I trim the stems that did not grow leaves?
    Community Answer
    If the pulp is brown, then that stem is dead and should be totally removed.
  • Question
    My rose is in a pot. Can it be planted in flower bed now?
    Community Answer
    Yes. I always use Quick Start and water the plant before I move it, then water with Quick Start for three days after planting. In my experience, the rose has no shock using this method.
  • Question
    Will roses turn dormant, or will they die?
    Community Answer
    They usually come back every year, so in the winter, they are dormant.
  • Question
    I recently planted new knock out rose bushes and they are drooping. The rose buds seem too heavy when wet and the stems are long so they bend and the bud are on the ground. Planted them last week. What should I do?
    CurtM
    Community Answer
    It sounds like there's an overabundance of growth on the bush. Try clipping a few of the flower clusters 6-8 inches below the blooms to alleviate some of the weight. Keep in mind that it's okay to remove as much as one-third to one-half of the plant's overall volume as long as you do it early enough in the spring for it to grow back.
  • Question
    Is it okay if my roses are very wooded at the bottom?
    Community Answer
    No, it's not okay. Trim off the wooded area as close to the new growth as possible.
  • Question
    While pruning in March, I saw black spots on the canes. Will these canes survive?
    Community Answer
    Eventually they will die off. Black spot is a fungi and needs to be removed as soon as you see it. Use a fungal spray every two weeks, and cut out all branches and leaves that have the black spots on them. Throw away everything you removed far away from any other roses or plants. The fungi spreads by spores, so keep the area beneath the rose bush clear of dead leaves. Use mulch to help keep the spores from getting on the bush. Clean your pruners before and after using them on black spot roses. The spores stay on the pruners and you can infect other plants and roses if you don't disinfect them. I understand that any household cleaner will work, or alcohol.
  • Question
    Our roses bloom several times all year long in Texas, but our bushes are not nice and thick. Should I prune them?
    CurtM
    Community Answer
    If your rose bushes haven't yet filled out and become lush, there's probably no need to prune them. However, you might do a little maintenance by removing overlapping or tightly-cluster canes and taking off a portion of the plant's overall height to keep it under control.
  • Question
    How can I get more flowers during the year?
    Community Answer
    Since roses bloom a lot, they use a lot of energy. Its best to fertilize 2 - 3 times with low-quality fertilizer, or once annually with a high-quality fertilizer.
  • Question
    What kind of fertilizer should I use on my knockout roses in the fall?
    Community Answer
    Any nutritious fertilizer will do. Just make sure it has all the nutrients the rose needs.
  • Question
    Can knockout roses produce new blooming shrubs from cuttings? I don't know if it's a hybrid rose, which I've heard may not bloom from cuttings.
    Community Answer
    Yes, roses are very easy to root from cuttings. They will bloom very nicely.
  • Question
    What type of fertilizer do I use after pruning?
    Community Answer
    Rosetone works great. After I prune, I fertilize with a handful of Rosetone on each bush.
  • Question
    My knockout roses seem to be bushy. The new branches are thicker than normal and a light green. Is this a disease?
    Kathie Kinsley
    Community Answer
    Check for thrips. They are not visible to us, but the damage is. Frilly new growth, light colored and weak stems are all signs. The buds will look different as well.
  • Question
    Do I cut the red stems that shoot up from a knockout rose?
    Community Answer
    No, the red stems are signs of new, healthy growth. Let them grow to full size and then prune to shape if necessary.
  • Question
    Can I cut knockout roses and put them in a vase?
    Community Answer
    Yes. I've done this and they lasted quite some time. I tried with unopened buds and it didn't work, though.
  • Question
    How do I get black spots off my knockout roses?
    Community Answer
    Clean up from the ground all of last year's mulch and dead dropped leaves. Sterilize your pruners. Prune off dead and diseased wood. Spray weekly with a fungicidal spray. Put down new mulch and dispose of all the old mulch and leaf litter off your property.
  • Question
    Should I prune the old rose buds?
    Community Answer
    Yes, as soon as they die. Do so with gloves and pruning shears. 1. Cut off the dead or ugly rosebuds at a 45 degree angle 1/4 inch above the next healthy looking set of 5 leaves. 2. Cut away the small bushy growth towards the bottom of the bush to increase airflow around the main strong stems. 3. Cut off any leaves that don't look immaculate. 4. New growth is reddish in color, so don't cut it off.
  • Question
    I live in Arkansas, can I still prune my knockout roses after first frost?
    Community Answer
    Yes, you can actually prune them any time during the year, but major pruning is done in the spring. We tend one bed that gets a 1/3 pruning in August and it does well.
  • Question
    I moved to new home in Florida with knockout roses that probably have never been pruned. How do I prune them?
    Community Answer
    Try doing a major "shaping " pruning now and then, in the spring, do a 1/3 to 1/2 pruning.
  • Question
    Should knockout roses be fertilized? When should they be fertilized?
    Community Answer
    Yes, all plants need fertilization. Give a good granular fertilizer application in spring and fall, and it can't hurt to shoot it with some liquid during the summer. Buy a good fertilizer developed for roses and follow the instructions on the label, you can't go wrong
  • Question
    My knockout roses are in the sun and I fertilize them but they have not bloomed in over three years. What should I do?
    Community Answer
    Give the a shock pruning, cut back to 12 - 16 inches leaving only 3-5 main canes.
  • Question
    What do I do if the leaves in the center of the bush are turning light green?
    Community Answer
    Check for insects or disease and treat if necessary. Also, test soil and amend if needed. And you could add some iron for a overall deeper green.
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