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help with knockouts

Discussion in 'Landscape Architecture and Design' started by clcscaper, Nov 13, 2008.


    KACYDS LawnSite Senior Member
    Messages: 559

    Chilli Thrips? Never heard of them before. Where they easy to kill? What did you use? Keep them in Lafayette, dont send them to New Orleans. Have enough problems already. lol:laugh::laugh:

    Learn something everyday........
  2. Lawnworks

    Lawnworks LawnSite Fanatic
    from usa
    Messages: 5,407

    When is the best time to prune knockouts? One of my neighbors, pruned her knockouts SEVERLY a month ago... I mean these were 4' tall knockouts about 3 years old, and they pruned them about 1.5' off of the ground leaving no foilage. I was amazed to see new growth a couple weeks ago. When I pruned mine that severely, it died!
  3. White Gardens

    White Gardens LawnSite Fanatic
    Messages: 6,776

    All roses are recommended to be cut back in the spring after they have began to bud out for the season.

    Fall cut backs aren't recommended, and that's kinda an old school method that is out-dated. Also, the only protection they need for the winter is a mound of mulch around the base to help protect the roots over the winter, and that's only for delicate antique varieties.

    Styrofoam cones and cages filled with leaves around the roses are a no-no.
  4. Lawnworks

    Lawnworks LawnSite Fanatic
    from usa
    Messages: 5,407

    How severly have you cut knockouts back? I am scared to prune them to where there is no foilage.
  5. White Gardens

    White Gardens LawnSite Fanatic
    Messages: 6,776

    My rule of thumb is if it's more than 1/4 inch in diameter in size (stem), then I leave it alone, unless I have Elmer's glue with me.

    If the stem is bigger than 1/4 inch, then it is recommended to put Elmer's white glue on the cut to seal it from infection.

    I always leave at least 12 inches of height when I cut roses back. After they have started to bud and fill out, I go back in and trim them to shape and take out any canes that are going the wrong direction.

    Cut angles, and distance to the next bud are also critical.

    Some roses I can cut back and not think twice about, and some I meticulously cut and clean my pruners with a light bleach solution after each plant is done so I don't transfer disease.

    I've seen some people cut their roses clear to the ground, but I don't unless I see new canes forming just above ground and I know for sure I'm going to get new growth.
  6. Lawnworks

    Lawnworks LawnSite Fanatic
    from usa
    Messages: 5,407

    With these red knockouts... I guess it is a crapshoot b/c they are not exactly a compact growing specimen. It seems to cut it down to 1.5', there will be no foilage... that is kind of why I am scared to prune so low. Elmer's glue... great suggestion.
  7. White Gardens

    White Gardens LawnSite Fanatic
    Messages: 6,776

    Crapshoot, I like that.

    The one thing I don't like about knockouts is that they don't seem to push up too many new canes every year compared to most traditional varieties. It seems like they just want to keep the same apical stem for their life cycle.

    Just go easy on them when pruning. Just like with any rose, wait until early summer to give them a detailed pruning, by that point you should be able to tell the health of the plant and how well it's growing. All in experience.

    When I prune all my roses for customers in the spring, usually I cut off most if not all the sprouting leaves. I only do this if I can tell for sure that there seems to be a good bud (red in color) on the canes to let me know that they will shoot out. The only real problem I've had with this is that I trimmed 15 rose bushes for a customer one spring and we had a really late freeze that killed back all the exposed canes. Luckily the roses were old enough and healthy enough that they snapped out of it no problems, they just started out much shorter than I like.

    Good luck, do some research on-line to see what other Knock-out enthusiasts do for pruning.
    Last edited: Nov 21, 2008
  8. PHS

    PHS LawnSite Senior Member
    Messages: 724

    Kris, PM me your email address and I'll send you some info on them. They were giving me problems on a few different plants, Knockouts, antique and climbing roses, Nandina, Plumbago, and Impatiens.

    I tried a variety of different materials that seemed to work ok but the bigger problem is they come back so fast. I would spray the plants, the next week they looked great with new clean foliage and the second week all the new growth is shriveled up and loaded with thrips. I think next year I'm going to treat them all with merit to try and slow them down and then alternate with Orthene and Conserve every two weeks.

    Along with that a lot of them are going to be dug up to really work over the beds and then replant them properly. Change the irrigation from overhead spray to drip, etc, etc.

    Around here it's recommended to do a hard pruning in August on knockouts. They way I do it is a heavy pruning in early January and then deadhead every two weeks through the growing season and then the cut back in Aug and then ride out the season deadheading as needed. For me that keeps them blooming strong all season.

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