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

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, deer or 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 rabbits too, 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 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 rust will 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 commercial fungicide. 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.

Knockout roses are wildly popular and have been for a while. Known to be a low maintenance prolific bloomer, you’ll find these beauties in most landscapes. While they are easy-to-grow and maintain, they do grow bigger each year and can get up to 6 feet tall and wide and are better suited to larger garden beds. They also have pronounced thorns which can make pruning painful.

Knockout roses are gorgeous. They are fragrant. They add color to your garden and if you are like most people who add them to your garden you look forward to watching them bloom each spring and continue their blooms throughout the summer and into the fall.

Unfortunately, for a lot of our customers they experience more frustration than joy while waiting for their roses to bloom.

There are several reasons why your roses may not bloom.

Not enough sunlight - These roses need a lot of sun. Unlike many things in life, this is quantifiable. Roses need at least 8 hours of sun a day. If there are nearby trees or shrubs that shade your rose bush for even part of the day, chances are they will not bloom well. In one case we realized that it was not a building or a tree that was causing a customer's problem but a van that parked in the same spot every day blocking the light for several hours of the day. Yes, these bushes are that picky.

Too much food - When you feed roses too much they will not bloom. They may become fuller with more healthy looking leaves but they will not bloom. Try not feeding them for a while and see if this helps. When you do feed them, start with a slow release fertilizer.

Improper watering - Knockout roses need to be watered from below. Watering them with a sprinkler may actually spread diseases such as black spot. Try to keep the leaves as dry as possible when watering.

Dry soil - In an earlier post we wrote about the benefits of mulch. Mulching around your rose bushes will help to hold in the moisture and keep it consistently moist.

Do you have beautiful knockout roses you would like to share with us? Do you have a secret to growing these bushes that was not mentioned above? Email us and let us know.


I did not know to prune my Knock Out® roses in early spring. Is it too late?

If they were just planted this spring and have already begun to bloom, we would advise against cutting them back hard. Try deadheading instead. If they have been in the ground a few years and are well established, it's okay to trim, but don’t take off more than 1/3 of the growth. Save the hard 2/3 trim until late winter/early spring.

Is pruning Knock Out® Roses the same as other roses?

Check your rose bush from time to time in late winter/early spring, and when you start to see new shoots growing from the canes on your rose bush, that’s a good sign that it’s time to prune. Cut back your roses (using hedge shears) to about 12". This should make them grow to about 3'-4' tall by the end of the season.

Is Knockout Rose Down for the Count?

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.

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.

Will Knockout roses grow in partial shade?

Unlike most roses which require at least six hours of sun, Double Red Knock Out Roses do fine in a location with as little as four hours of sun. A moist, well-drained soil is ideal. This rose loves morning sun and afternoon shade and does not require any dead-heading, meaning old blooms do not have to be removed.

Secondly, where is the best place to plant knockout roses? Double Knock Out roses are very easy to grow. Give the plants full sun in a garden spot with fertile, well-drained soil and space them about four feet apart to allow good air circulation. To keep the blooms coming, fertilize your Double Knock Outs after every bloom cycle with any good rose fertilizer.

Subsequently, one may also ask, what Roses grow best in shade?

Floribunda roses are an excellent choice for partial shade areas in your garden. they are known for their sprays of color and the number of blooms they produce. Floribundas may not produce as many sprays as they do in full sun, but expect those pictured below to perform quite well in partial shade.

Can roses grow without sunlight?

No rose will thrive and bloom without some sun, but there are some roses that will do just fine with a little shade.

Watch the video: MY AMAZING KNOCKOUT ROSES. mommyCelle