Knockout roses not blooming

Summer Care For ‘Knock Out’ Rose

‘Pink Knock Out’ Rose Van Chaplin

Compared to other roses, ‘Knock Out’ is pretty idiot-proof. It’s tough, grows in almost any well-drained soil in a sunny spot, and doesn’t need spraying for black spot fungus, the universal bane of rose lovers. But a rose you can just plant and forget? Forget about it.

For one thing, if you want to keep it blooming continuously, you need to groom it. This means clipping off the faded flowers. If you leave them, they’ll form rose hips with seeds inside and flowering will slow to a crawl. Grooming ‘Knock Out’ rose every week or so spurs new growth loaded with new rose buds.

Second, ‘Knock Out’ may start out small and compact when you buy it, but it won’t stay that way forever. Unless it dies, it will get bigger and bigger every year. A neighbor of mine has hedge of ‘Knock Out’ rose that’s now pushing six feet tall. If this is too big for the space you have, you’ll need to prune. Fortunately, ‘Knock Out’ blooms on new growth, which means that you can prune it just about any time of year. Be sure to wear leather gloves, though, as it’s one of the most viciously thorny plants you’ll find. You can cut it down to a foot tall if you want. In response, it’ll send out lots of new growth and blooms.

Third, just because ‘Knock Out’ doesn’t need spraying for black spot doesn’t mean you don’t occasionally have to spray for other things. In hot, dry weather, tiny spider mites on the undersides of the leaves may suck out the sap, causing the leaves to look speckled or bronzed. Then you’ll need to spray with horticultural oil or insecticidal soap. Spraying the foliage with a jet of water also works, because spider mites love dry foliage and hate wet foliage.

Another problem that’s common around this time of year is leaves dotted with small holes. They look like someone fired a shotgun at them. The culprit is a sawfly that lays tiny eggs on the undersides of the leaves. The eggs hatch into larvae called rose slugs that chew away at the leaves from the undersides, leaving little “windows” and holes. Spraying the leaf undersides with neem oil will control this. Neem oil also works against another insect pest that likes to eat ‘Knock Out’ rose, the Japanese beetle. Just don’t spray the flowers, as neem is toxic to bees.

Does ‘Knock Out’ need less care than most other roses? Definitely. Will it look good if given absolutely no care? Definitely not. Now you know.

Knockout Roses- Keep ’em Flowering All Summer Long

Knockout Roses are just that-a splendid profusion of blooms which we can enjoy all summer long. At the “Wayne Bed & Breakfast Inn”, I have had gorgeous bushes for the past few weeks, which are now not at all as interesting with the browning remnants of the spent roses.

If you wait long enough, the withered roses fall off all on its own, but new blossams are delayed in comparison to new growth with deadheading. So, you can help nature by deadheading the roses as soon as the rose has withered. With the deadheading you not only will get flowers faster, but by staying steady to this task, you will have roses into the fall. . . with a third or fourth flowering.

If you attempt to pull off the withered blossam, you might tear this stem. It is much better to deadhead the knockout roses with the use of pointy-nosed scissors.

Here’s how: Follow the stem to the intersection of the first new bud, and snip as close to this bud as possible without clipping the new growth. With a little practice, you can snip and pull in one, clean motion.

Do not confuse deadheading with pruning. This is not any aggressive cutting of the cane of the rose bush, but simply removing the deadened, browning flower.

This will take some time and effort. However, the reward of spectacular roses all summer long is more than worth it.

If you have any tips about caring for your Knockout roses, please share them. More photos of the roses in bloom can be seen at my website:

Why Won’t My Knock Out Roses Bloom?

The main reason roses don’t bloom is they aren’t getting enough direct sunlight. You say your plants are in full sun, but keep in mind they need at least 8 hours of direct sun a day. If there’s a tree or building nearby, they might not be getting enough light. Also, don’t go heavy on the fertilizer. Roses do like to “eat,” but if you feed them too much you’ll encourage them to grow only foliage. I suggest you hold off on feeding them at this point. In my garden, I prefer a slow-release fertilizer such as Osmocote that feeds the plants at a regular rate, not all at once.

Also, do not let your roses get wet from those sprinklers. Lawn sprinklers are a good way to spread fungal diseases such as Black Spot. The best way to water roses is from underneath, keeping the foliage as dry as possible. Knock Out roses aren’t as prone to Black Spot as other roses, but if the foliage keeps getting wet, they can get the disease. So, here’s the deal: Make sure they are getting plenty of sunlight, back off on feeding them too much, and mulch them to keep soil moisture consistent and stop the sprinklers from hitting the foliage.

My Knock Outs aren’t so “knock-out” anymore!

By Monica Laliberte

I LOVE to work in the yard. O-K.. I LOVE it depending on the task. For example, I like to TRIM bushes– but I don’t like to actually PICK-UP the trimmings! I like to PLANT flowers, but I don’t like to CLEAN UP the dirt left all over the deck when I’m done! Thank goodness my husband is always willing to pick up after me!

Anyway– some of my favorite additions to my yard in recent years are my Knock Out roses. They’ve been a dream for a do-it-yourself landscaper like me who sometimes has a thumb that’s a little more lime colored than dark green! That’s been until the last couple of weeks– when they suddenly stopped blooming! I’ve been pondering the problem until Gary Pierce, a Horticulture Extension Agent in Harnett County– came to the rescue with the following e-mail! And I encourage anyone who likes gardening to get on his “list.” His “Ask the Hort Agent” e-mails are always informative and entertaining!

Ask the Hort Agent

Why have my Knock Out Roses Stopped Blooming?

Before you throw in the white towel, give the plant a standing 10 count. The ‘Knock out’ Rose is a group of hybrid shrub roses bred to require less maintenance with greater disease resistance and cold tolerance. In 2000, the original Knock Out Red was introduced and won the All American Rose Selection Award. Since this time, Knock Outs have become best sellers.

These roses usually bloom like a house on fire the first and second year. Sometime between years 3 and 5 they get so big they can run out of resources to keep them blooming. Roses need 3 things to bloom: sun, water and fertilizer.

Most roses need 8 to 10 hours of sun every day. Knock Outs can thrive on half that. This is a mixed blessing. Some people interpret this characteristic as a shade plant. Knock Outs are still sun plants. They do best in the sun. Less sun equals less blooms. Extended cloudy weather is also not conducive for flowering.

Give roses a minimum of 1 inch of water per week, and keep it off the foliage. Make sure your soil is well drained. They don’t like to stand in water.

Sometimes low potassium can contribute to blooming issues. High phosphorus rates encourage flowering and a strong root system. Differences in soil consistency may account for differences in plant responses to equal fertilization. Take soil samples to make sure your nutrient levels are appropriate in all flower beds. Slow-release fertilizers and/or compost offer a continuous supply of nutrients. Knock Outs continue to produce new flowers throughout the summer, but a little extra fertilizer may produce even more roses.

If you are supplying these things, try pruning them back about 10-20 percent. You can prune any time of year. Another characteristic bred into this rose was the ability to drop off its dead blossoms. In other words, Knock Outs don’t have to be deadheaded. While not needing to deadhead roses is a good quality, it can also slow down the ability of the rose to bloom again quickly. If you want to keep your Knock Outs blooming as often as possible, snip off the old blooms. Even though they will eventually drop their dead blossoms, you can get ahead of the game by helping them out.

When I hear knockout, I think UFC (mixed martial arts). I visualize Chuck “The Iceman” Liddell in my yard pounding on my rose bushes. When he gets through with them, I won’t have to worry about blooms ever again.

Gary L. Pierce
Horticulture Extension Agent
Harnett County

Kiss From a Rose Songtext

von Seal

Ba-da-da, ba-da-da-da-da-da, ba-da-da
Ba-da-da, ba-da-da-da-da-da, ba-da-da
There used to be a graying tower alone on the sea
You became the light on the dark side of me
Love remained a drug that’s the high and not the pill
But did you know that when it snows
My eyes become large and the light that you shine can be seen?
Baby, I compare you to a kiss from a rose on the gray
Ooh, the more I get of you, the stranger it feels, yeah
And now that your rose is in bloom
A light hits the gloom on the gray
Ba-da-da, ba-da-da-da-da-da, ba-da-da
There is so much a man can tell you, so much he can say
You remain my power, my pleasure, my pain, baby
To me you’re like a growing addiction that I can’t deny
Won’t you tell me, is that healthy, baby?
But did you know that when it snows
My eyes become large and the light that you shine can be seen?

Baby, I compare you to a kiss from a rose on the gray
Ooh, the more I get of you, the stranger it feels, yeah
Now that your rose is in bloom
A light hits the gloom on the gray
I’ve been kissed by a rose on the gray
I’ve been kissed by a rose on the gray
I’ve been kissed by a rose on the gray
(And if I should fall, would it all go away?)
I’ve been kissed by a rose on the gray
There is so much a man can tell you, so much he can say
You remain my power, my pleasure, my pain
To me you’re like a growing addiction that I can’t deny
Now won’t you tell me, is that healthy, baby?
But did you know that when it snows
My eyes become large and the light that you shine can be seen?
Baby, I compare you to a kiss from a rose on the gray
Ooh, the more I get of you, the stranger it feels, yeah
Now that your rose is in bloom
A light hits the gloom on the gray
Yes, I compare you to a kiss from a rose on the gray
Ooh, the more I get of you, the stranger it feels, yeah
Now that your rose is in bloom
A light hits the gloom on the gray
Ba-da-da, ba-da-da-da-da-da, ba-da-da
Now that your rose is in bloom
A light hits the gloom on the gray

Knock Out Roses Won’t Bloom – How To Get Knock Out Roses To Bloom

We buy rosebushes typically for the beauty their blooms will add to rose beds, gardens or landscaped areas. Thus, it is cause for major frustration when they do not bloom. In some cases, roses will form nice big buds or clusters of buds, then seemingly overnight the buds appear to wilt, turn yellow and fall off. Knock Out rosebushes are no different when it comes to this frustration. There are several reasons why these roses may not bloom, so let’s take a look at some of them.

Why are Knock Outs not Blooming?

Figuring out how to get Knock Out roses to bloom means finding out what’s causing them not to flower in the first place.

Animal pests

Are buds on the roses one day and by next morning totally gone? Maybe they’re lying on the ground, as if cut off, or perhaps missing altogether. The culprits here are usually squirrels, deeror elk. Deer and elk may eat just the buds off first with a small amount of foliage, returning another night to decimate the bush. I am not sure why squirrels will sometimes cut the blooms off, leaving them lying about and not eating them. Perhaps, their plan is to come back later for them.

The use of a liquid or granular repellent may give some relief but you need to keep on top of applying the products for them to work their best. That said, these repellents can work well for the squirrels, and rabbitstoo, if they are eating the foliage. Building a fence around the rose bed or garden can help, but many times must be an electric fence to be very successful as hungry deer and elk will either jump over the fence or push it down in places.


Tiny insects, such as thrips, can bore into rosebuds and will cause them to fall off without blooming. To truly get at such insects, one must use a systemic insecticide listed for their control.


If Knock Out roses won’t bloom, they may not be getting enough sunlight. Make sure when planting them that they get 6 to 8 hours of sun. Take a good look at the proposed area of planting at different times of day to see if any trees or buildings shade the area. Some shade where partial sun is available can be a good thing during those hotter days of summer, as it provides some relief from the intense sun and extreme heat.


Be sure to feed your roses with fertilizers that build the soil or root zone your Knock Out roses as well as feeding the upper parts of the rosebushes. Repeated high nitrogen usage will cause major foliage production with little to no blooms on Knock Out roses. High nitrogen fertilizers can also be the cause of a condition called “Crooked Neck” on roses. The forming bud tilts to one side, sometimes drastically. The bud may open and the bloom be crooked and malformed or may not bloom at all.


Along with the proper feeding, make sure your roses are watered well. Lack of water, especially on hot summer days, doubles down on the stress factor the rosebushes must deal with. Stresses and shock will cause Knock Out roses to stop blooming and become more susceptible to fungal or disease attacks.


Fungi such as black spot, powdery mildew and rustwill stress rosebushes and stop the blooming process even in the formed buds stage. Spraying roses on a scheduled basis with a fungicide may be in order. There are many no-spray gardens out there that are lovely and perform very well. In the no-spray gardens, one must be very careful to obtain rosebushes that have been proven to be high in disease resistance in varying weather conditions/climatic conditions.

In my rose gardens, I have chosen to use a very good earth-friendly fungicide called Green Cure. Using the product at the rate noted on the label will indeed cure any fungal problems. Choosing earth-friendly products to spray for any pest problem as a first choice is best, as harsh chemical sprays can simply add to the overall stress, thus limiting bloom production.


Even though one of the big selling points for Knock Out rosebushes is that they are self-cleaning, trimming off the old spent blooms “precisely” below the base of the old bloom will encourage bloom production.

Why Some New Roses Are Slow to Start and What to Do About It

Recently on our discussion forum a question was asked why some newly planted roses were starting to actively grow and some were just sitting there doing nothing. They were all planted at the same time and treated the same way. The ones doing nothing are still green and don’t look dead, they just aren’t growing.

It’s a legitimate question, and frankly something I’ve met with off and on over the years myself. I’ve frequently planted even roses of the same variety side by side only to see some take off and some languish. I think the tendency when coming across this for the first time is to panic and think you are doing something wrong. The response is frequently fertilizing more heavily or watering more. In all honesty the last thing you should be doing.

Let’s start with some ideas why I suspect this happens. Notice I used the world “suspect.” I’ve never seen a study on this so instead these are just some thoughts of my own.

We’ve talked in the past about roses harvested from a field being held in cold storage until they are shipped. We talked about them drawing on their reserve of starches to stay alive during that period. The longer the rose has been in cold storage the more starches it uses, and so the less it has available when it’s planted to emerge from dormancy. Emerging from dormancy simply means it starts to actively grow and produce roots and leaves.

When you buy several roses it is very likely some have been in cold storage longer than others. I’ve found the longer a rose has been in cold storage the slower it starts to grow. I think that’s what happened in this case.

So what can we do about it? If it happens in your garden after you’ve bought the plants the best course of action is to do nothing. Fertilizing won’t help and neither will additional water. I feel adding more water might hurt it because if the rose is not actively growing, it’s not taking up water and you may drown it. Additional fertilizer may push it too fast and burn it out. Let nature’s natural rhythms wake it up.

I will advice you to make note of which roses are not growing and even take some photos. Good Garden Centers stand behind their products and if the rose never starts to grow they will replace it. However, you need to have evidence.

The above is a likely scenario with mail order roses where you can’t see them before you buy them. If you buy roses locally in pots to help avoid this make sure to look for roses that are actively growing. If you buy bareroot roses locally, look for ones with the bud eyes starting to swell or even pushing small growth. Avoid bareroot roses with leaves on them because in my opinion they are too far ahead of themselves in pushing new growth. Frequently when you plant these roses the leaves die and rose often follows because there is no root system to support that top growth.

If you come across this in your garden, don’t panic. You are not alone and I suspect almost every rose grower has had this happen over the years. Keep in mind it’s likely you’ve done nothing wrong. It’s just that some roses, like people, simply take longer to get up the morning!

Happy Roseing


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