My knockout roses are not blooming properly

phloro(8)June 19, 2012

My double knockout rose plant had large beautiful blooms when I first bought it. After I planted and fertilized them (with a rose fertilizer) I was expecting the next flush of blooms to be as good as the original ones when I bought the plant. Unfortunately the "double" knockout roses looked like single knockouts and a size smaller ! and some of them did not bloom properly or were deformed. The plant itself looks good with nice foliage and is sprouting pretty well. Can't say the same for the roses. I fertilize every week alternating between a rose fertilizer and a bloom booster (with high phosphorus content). The drainage is very good, gets watered regularly, gets > 6 hrs sunlight. What am I doing wrong ?? any advice you may give is highly appreciated.

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dublinbay z6 (KS)

I'm not an expert on this subject, but my guess is that you are drastically over-fertilizing that poor rose bush if you are feeding it every week. That is far too much food in general and certainly much more phosphorus than it needs.

At most, rose foods will usually say something like feed monthly, and I would guess most rose gardeners work on a feed schedule of once in the early spring and then after each bloom cycle. Some rose gardeners claim they have amended the soil and other than adding manure around the rose once a year, they do no other feedings because the soil has enough nutrients in it already.

Once you have overfed a rose, the only solution I know is watering it thoroughly in hopes of flushing out some of that excessive food. Perhaps other posters will have other suggestions.

You really need to relax with your rose. Knock Outs (and many other roses) can do a pretty good job of taking care of themselves most of the time. Giving them water when they are dry and it hasn't rained may be your most important job as a rose gardener.

Good luck.


    Bookmark   June 20, 2012 at 8:23AM
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michaelg(7a NC Mts)

Everything Kate says is true. I would add that "bloom-buster" fertilizers are useless, and the excess phosphorus can do harm by tying up other nutrients. This may be what is wrong. Your rose fertilizer applied as labelled will supply probably 3x as much phosphorus as the plants can use. Any applied phosphorus will stay in the soil for decades.

    Bookmark   June 20, 2012 at 10:41AM
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diane_nj 6b/7a

Agree, stop fertilizing. They actually do better with some neglect, twice - three times a season with a good organic-based fertilizer should be enough. But, you've given more than your young plant can even try to use, it doesn't have the root structure to take in all of those nutrients. Clip off the old blooms. Then wait. Your plant isn't mature, and it needs to grow roots in order to bloom properly.

    Bookmark   June 20, 2012 at 11:08AM
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Hi kate, michaelg & diane

Thank you very much for your advice ! you have no idea how much this means to me as I am a novice gardener and have been enjoying it a lot.

Yeah now that's easy to do...not overfertilizing them. Thought I had to do some complex procedures to get large blooms. Being new to all this, I have been over zealous with all of my plants and have been pretty heavy handed with the fertilizers. At times I even fertilize them twice a week!!!

btw I was wondering if using spent tea leaves on my rose bushes would be ok ??? I mean I've seen them being used around rose bushes, though I dont know what purpose it serves.

Once again thanks sooo much guys for saving my roses :)

    Bookmark   June 20, 2012 at 11:34AM
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michaelg(7a NC Mts)

Spent tea leaves and coffee grounds are fine.

    Bookmark   June 20, 2012 at 11:38AM
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Another possible reason your blooms aren't as nice as they were is that it's late June and you live in Texas. Rose blooms don't look as large or full when it is really hot.

    Bookmark   June 20, 2012 at 12:26PM
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hoovb zone 9 sunset 23

And...sounds like these are newly planted, so they are young? They need to settle in and grow a nice big root system in the soil and then they will perform as expected, or even better. Young newly planted roses can't do what a well established plant can. They need to get used to their new surroundings: to the soil, to the water, the light, the heat, the rhythm of the seasons in that particular spot...

    Bookmark   June 20, 2012 at 4:15PM
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Yeah that might also be the case...been only 3 weeks since I planted them. They're just beginning to sprout new branches. Guess I can't expect too much too soon :) Thanks

    Bookmark   June 20, 2012 at 7:56PM
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My knockout roses are doing GREAT !! they're big and full and abundant on the bushes...gorgeous. I just let them be, they're doing just fine. Thanks all for the advice.

    Bookmark   July 2, 2012 at 12:34PM
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dublinbay z6 (KS)

That's wonderful, phloro! Relax and enjoy your roses--now what better advice could anyone receive! : )

Thanks for giving us an update.


    Bookmark   July 2, 2012 at 3:36PM
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hoovb zone 9 sunset 23

Great news, and as they become more and more established, they may be even better.

    Bookmark   July 4, 2012 at 11:45AM
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