Is Knockout Rose Down for the Count?

April 21, 2013 | By | Comments (29)
Knockout rose

Enough color to knock your socks off — that’s ‘Knockout’ rose. Photo by Steve Bender.

Introduced in 2000, ‘Knockout’ rose quickly became the best-selling landscape plant in the country. It had everything — showy, continuous blooms; compact growth habit; tough-as-nails constitution; and, best of all, no need to spray for black spot disease. But now, nature has tossed green kryptonite into Superman’s garden. And ‘Knockout’ rose may just get its bell rung.

A Deadly Threat
‘Knockout’ rose (the original single red, shown above, plus a bunch of newer colors) owes its uber-popularity to the belief that it’s the first “no maintenance” rose — perfect for the lazy gardener in all of us. People think it needs no watering, spraying, pruning, or fertilizing — EVER. It’s like an actual living plastic plant. You just stick it in the ground and it will bloom, bloom, bloom with zero care from you. How marvelous.

Unfortunately, this belief is dead wrong. ‘Knockout’ does need water, fertilizer, and pruning. And now it’s facing a disease so serious that its very survival is in question. Rose rosette disease.

Rose rosette

Rose rosette disease. Photo: nicolewardukblogspot.com

This is what rose rosette looks like and it’s not pretty. A formally healthy plant starts producing Medusa-like bunches of bright-red new shoots. The shoots bloom, but the flowers look distorted. As rose rosette spreads through the plant, the rose gradually dies back, until it completely croaks. Down for the count.

What Causes Rose Rosette?
Rose rosette is caused by a virus first discovered in the western U.S. around 1940. The virus is principally spread by tiny eriophyid mites — so tiny, in fact, that they literally blow into gardens on the wind. When they feed on a rose, they transmit the virus. At that point, the jig is just about up.

Now here’s a surprise. There was a time when rose rosette was considered a savior, not a plague. Any of you remember the infamous “living wall,” aka the multiflora rose? A vigorous, arching import from Japan, it produced pretty white flowers in spring and thousands of small, bright-red rose hips in fall. It grew so thickly that highway departments in the East and Midwest actually planted rows of it down highway medians. Even a tractor-tractor couldn’t smash through. Cattlemen also used it to contain cattle.

But you know what they say about good intentions. Birds ate the red rose hips and spread multiflora rose everywhere. It proved to be an awful, noxious weed. States banned it, but it was too late. The entire eastern U.S. was destined to be smothered by the stuff, unless a control could be found.

It was. Rose rosette disease.

Wahoooo!!! Rose rosette killed multiflora rose faster than a van filled with nuns kills a good kegger. Unfortunately, when rose rosette ran out of multiflora roses, it looked for something else to feast on. The target? ‘Knockout’ rose and other shrub roses. The first ‘Knockout’ roses to show symptoms were located where the highest concentrations of multiflora roses were growing — the East and Midwest. ‘Knockout’ roses in the South have it now too.

Can Anything Stop Rose Rosette?
Because rose rosette is caused by a virus, it eventually spreads internally to every part of the plant. Promptly removing the bright-red shoot clusters by cutting through healthy green wood below them may save a rose. But once a rose gets full-blown rose rosette, turn out the lights. You must pull up the rose, roots and all, bag it, and throw it out with the trash. Spraying will not work.

Conard-Pyle, the respected Pennsylvania nursery that introduced ‘Knockout’ roses, suggests pruning back the plants by 2/3 while they’re dormant in late winter to remove any overwintering mites and eggs in the bud crevices. This is especially important for large landscape plantings of ‘Knockout,’ because the more bushes you have, the more mites you have, and it’s easier for the virus to spread.

Now For Some Really Bad News
According to Grumpy’s sources, most rose species and their selections are vulnerable to rose rosette — not just ‘Knockout.’ So if your love your roses, keep your eyes peeled for weird-looking, bright red shoots. Don’t leave yourself open to a ‘Knockout’ punch.

COMMENTS

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  3. Jan Binder

    I’ve been wondering what this funny new growth and wierd blossoms were on my mother’s Knockouts…She’ll be so disappointed as she’s in a nursing home and she keeps asking how they’re doing…I thought they were doing well as I trim them back often and they’re blooming great…so sad…but thanks again for the verdict!

    July 1, 2014 at 1:25 pm
  4. Manalto

    I suppose there can. (?)

    June 23, 2014 at 3:41 pm
  5. Steve Bender

    Manalto,

    In that case, they can wear a jacket with no tie.

    June 23, 2014 at 3:31 pm
  6. Manalto

    A “formally healthy” plant? What about plants that are casually healthy?

    June 19, 2014 at 2:34 am
  7. Posts from the Weekend | smithposts…

    […] and keep on blooming, or so I thought when I planted them.  Then the Grumpy Gardener from  Southern Living burst my bubble in the linked article “Is the Knockout Rose Down for the Count?” So far so good […]

    June 14, 2014 at 3:21 pm
  8. Steve Bender

    Sue,
    I don’t know of any rose that is immune to rose rosette. So don’t replaced diseases roses with more roses or they’ll just get it too. I don’t know of any flowering shrub that does what a rose does, but you might consider hydrangeas or dwarf butterfly bushes.

    June 12, 2014 at 2:38 pm
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    June 11, 2014 at 6:25 pm
  10. Sue

    Steve,
    Would you replace knockout roses when you remove those with rose rosette? I have heard the new plants will only pick it up from the soil again. If not knockout roses, what other flowering shrub would be a good replacement?
    Thanks.
    Sue

    June 11, 2014 at 12:50 pm
  11. Mary

    I am very sad. Looks like we will have to dig up and toss out 6 rose bushes. This overtook my roses very quickly as they were beautiful about a month ago–no sign of this disease.

    June 8, 2014 at 9:02 pm
  12. Steve Bender

    Ellen,

    My advice to you is to order a copy of the Southern Living Garden Book from amazon.com. It’ll tell you what you need to know.

    May 8, 2013 at 11:39 am
  13. Sudden Death of Roses…why? – Trees, Grass, Lawn, Flowers, Irrigation, Landscaping… – Page 2 – City-Data Forum

    [...] Here's Southern Living on the disease. Very sad. I might still give one or two a try but pot them in enormous pots and not make a big commitment. A good picture also to help identify: Is Knockout Rose Down for the Count? – The Daily South | Your Hub for Southern Culture [...]

    May 7, 2013 at 8:15 pm
  14. Ellen Huber

    Hi Ya’ll
    I just purchased a home in northern SC, which has …….. 61 KNOCKOUT ROSES!
    Having moved here from northern Wisconsin (where temps range from -40* to 90*) in Feb, I had never heard of these beautiful roses. Roses are very difficult to grow that far north due to the harsh winters, and sand for soil.

    I am so grateful to “THE GRUMPY GARDNER” for writing this article. I know nothing about roses!!! I am very well educated on gardening in zones 4 & 5, but zones 7 & 8, I am clueless! Heck I can’t even identify 9/10ths of the plants, trees, & shrubs (boy do I have shrubs – former owner went crazy). To give you an idea of the enormity of my gardens I have a 16 zone irrigation system. With that being said, I am spending a lot of time educating myself, but I feel so very overwhelmed, because former owner moved out in November & the weeds are now out of control & the shrubs are over grown. Throw into this state of disarray: I was just told we have CENTIPEDE GRASS in front yard & BERMUDA in back. AGAIN I AM CLUELESS, I have never before heard of centipede grass. Both yards are filled with patches of clover, & creeping myrtle – UGH!!! IT LOOKS AWFUL. Our property is 2.5 acres. I DON’T KNOW WHERE TO BEGIN…….

    I sure can use some advice, along with a list of resources, and products to use, (weed control, fertilizers, books, etc.). I will say this I am petrified about my roses getting RRD, as I noticed one smaller bush is completely dead. Will inspect them all as soon as the down pour stops.

    THANK YOU SO VERY MUCH for taking the time to read this very long post & THANK YOU in advance for your responses.

    Ellen

    May 5, 2013 at 8:53 am
  15. Deby Wine

    I was sad too Beth. I have mine in a large bed at the front of my townhome, under my kitchen window. I am digging it out today. I located a dwarf lilac shrub that grows 4 X 4 feet, and I will be in 7th heaven when this fills in the space. Prairie Petite from ForestFarm.com I have a small yard, so each plant must be special. I was told by a local wonderful garden center that this virus will not effect future palnting of another variety palnt, is spread by beetles, but the disease is always terminal. Always wanted a lilac, but they grow too large for my front yard. I started to google varities, and found a new dwarf variety. Called all over the counrty, but finally found them at Forest Farm in Oregon. Placed my order yesterday! Good luck with your garden..deby

    April 27, 2013 at 11:59 am
  16. Beth

    i’ve got five knockouts that are 6′+ tall, and equally as wide, about 7 years old. I couldn’t figure out what was going wrong with them this year until i saw this… i’m so sad. They were beautiful until this past fall when they started making these crazy dark red knots of stems, one of them doesn’t have them yet, but the other four are COVERED. I wish there was a way to save them. :(

    April 27, 2013 at 11:25 am
  17. Deby WIne

    I put in a Knockout Rose 3 years ago. THe first year was just wonderful, and I thought about a row across my entire large raised flower bed on the front of my townhome. Next year things started out well, but quickly became evident that my plant was “off”. Last year it was awful. Deep red foliage that had no traditional growth habit, and no flowers. It looked like the plant was attacked by some insect and was damaging its growth. Now after finding this post on fb, I see what the problem is. My plant is doomed with this disease. I plan to dig it out today, and will never buy this plant again. $25. for one years of good growth..never worth the risk again. I almost put these in our community behind our large wooden sign. (HOA Pres.)

    April 25, 2013 at 9:01 am
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    April 24, 2013 at 9:57 pm
  19. Steve Bender

    Erin,

    The new foliage of roses in spring is usually reddish, but then it turns green. Red growth occurs all over the plant. With RRD, the reddish shoots occur in weird, bunched clusters called “witch’s brooms.” And the foliage and shoots stay reddish until they die.

    April 24, 2013 at 8:50 am
  20. Erin H.

    How can you tell the difference between normal new growth which is red in color and diseased shoots that are affected by rose rosette?

    April 23, 2013 at 5:49 pm
  21. Carolyn Binder

    Pruned mine back hard this spring, and they look healthy so far. I’m more worried about my beautiful climbers. Thanks for the info–I’ll stay on the lookout for RRD.

    April 21, 2013 at 9:14 pm
  22. Dee Nash

    I’m so glad you’re spreading the word too. I’ve written about Rose Rosette twice in the last couple of seasons, and I’ve lost several roses to it. The good news is I’ve found lots of other plants I really like in place of the ones I’ve lost. When I first identified RRD on ‘Zephirine Drouhin’ and ‘New Dawn’ I dug both of them and threw them away. I also didn’t plant any roses in the same spots. So far, my Knockouts are fine, but mine aren’t planted right next to each other like they highway department plants them. I also grow a lot more of the pink which doesn’t seem as susceptible. There is no good reason why. I also prune all of my roses, being careful to bleach my pruners in between shrubs. You know I also water and feed them. On second thought, maybe that’s why. Thanks again for spreading the word. I hate RRD with a passion. One more thing . . . a lot of nuns drink. You’d like partying with them. LOL!~~Dee

    April 21, 2013 at 4:51 pm
  23. Carolyn Choi

    I think that’s what mine had last Fall and before you even told me I had the good sense to cut them back in early winter and I sprayed them with a 3-in-1 Fungicide, Miticide and Insecticide. They look great now so I guess this treatment worked – plus we had a cold winter ( by Carolina standards ) which may have helped kill the mites.

    April 21, 2013 at 4:42 pm
  24. Freda Cameron

    I cut mine back hard in late winter and so far, so good…but, with this late spring, they’ve not yet budded up to bloom. Time will tell.

    April 21, 2013 at 3:02 pm
  25. Terri Willoughby

    This disease, aka “witches’ broom” attacked my 5 1/2′ tall pink knockout rose last season (which was 8 years old & glorious!) and alas, we had to dig it out, roots & all, bag it, & cart it off to the dump…sad day! And oh, by the way, do not try to plant another knockout rose in the same spot…bad idea! The soil is now contaminated and big chance your new rose will get it also. Find another spot for another rose & pray that it doesn’t get all of our knockouts! Just when we thought we had the perfect rose…unfortunately, no such animal…er, plant! :)

    April 21, 2013 at 12:12 pm
  26. Christopher C NC

    Rose rosette disease is epidemic in Haywood County NC where we have whole mountains covered in multiflora rose. This is a disease of ALL roses, not just knockouts or shrub roses. ALL roses.

    April 21, 2013 at 12:00 pm
  27. Barbara Whitehead

    This could be a real bummer.

    April 21, 2013 at 11:50 am
  28. Katy

    Thanks for this information! We have 6 that were part of the foundation plants on our new construction home. I’ll be sure to keep an eye out this year and to trim back over winter as suggested.

    April 21, 2013 at 11:48 am
  29. Maureen

    Sad news. I will be on the lookout. On another note, the article states, “A formally healthy plant…” It should say “formerly”, not “formally”.

    April 21, 2013 at 10:56 am

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