Double Knock Out Rose Problems

Nice & Easy Double Knock Outs by perennialpal

TheGardenLady received this question from Wendy.

I live in eastern North Carolina and I have several double knockout rose bushes and they have been beautiful. This year I pruned them back in early spring and had a magnificent show – we have had several hard storms lately and now there are no blooms on the bushes. There are a lot of dead heads. Should I pinch off all of them or should I leave them be? I dont remember having to do this after first pruning in the past – but I also thought I had more blooms and for a longer time through out the summer.

When one has a hard rain it knocks a lot of flowers off. The rain did a job on my peony flowers as well as my Knock Out Rose flowers. Perhaps someone should invent a rose umbrella to protect the flowers from hard rains. They do sell umbrellas for Peonies – but these umbrellas are really to protect the peonies from too much sun. Cricket Hill Nursery sells peony umbrellas from Japan (see here).  Too much sun will make the peony flower have a shorter bloom period. So gardeners do have to work with the elements.

Back to your roses. Knock Out Roses are bred to not have to dead head them.  See here.  The petals pretty much fall cleanly off. But I think the part that is left does not look pretty, so I cut it off back to some leaves.  It seems much cleaner looking to me. You will have to decide what you want to do – to dead head or not to dead head. Just know that you don’t have to deadhead. I let the rose rest a little after its initial burst of blooms. The next time I have to water the roses, I add a little fertilizer that has a high phosphorus content to the water in a watering can and pour it around the roots of the bush.

I loved Schultz’s Bloom Plus which had the highest phosphorus percentage; but Schultz gave up this fertilizer component of their products. I was so upset to learn they no longer are making their Bloom Plus nor did they tell me if any other company has taken over the manufacture of it. So I went to all the local nurseries to see if any had this Bloom Plus product left on their shelves. One of the best nurseries in my area, knowing how good the product was, had ordered a lot; so I bought up a lifetime supply- it doesn’t spoil and one uses so little of it per gallon. Of course, there are other brands that make rose fertilizer or fertilizers for optimum flowering of plants. I just never thought they were as good as Schultz’s.

Double Knock-Out Roses by Charity D

I have seen that with this added fertilizer encouragement each time I water my roses, I have a great flower show. But even without the extra fertilizer boost, Knock Out Roses will delight you with continuous bloom throughout the summer. Just let it catch its breath.

Roses in TheGardenLady’s Garden

Welcome to TheGardenLady’s garden. I will be posting some photos of plants in my garden. I had hoped to send you photos as each plant flowered. But the season is passing quickly and so many of the flowers, like my Jacob’s Ladder-Polemonium and bleeding hearts-dicentra have already finished blooming in my yard. So I am posting photos of some of my roses.

This year TheGardenLady’s roses are blooming their heads off. They are so lush with flowers that the branches can barely support them.

There are two Knock Out Rose Rosa ‘Radrazz” and the Pink Knock Out Rose, Rosa ‘Radcon’.  I have had these roses for a few years. The last two years I have pruned these two rose bushes in early spring. I mulch the bed they are in with aged horse manure. I see that the roses get water if there is a heat wave or drought. When I water I let the hose run near the roots and soak the roots. I do not spray water over the leaves.

Continue reading “Roses in TheGardenLady’s Garden”

Do You Dead-Head Encore Roses?

Gotta love those knock-outs!!! by perennialpal

TheGardenLady received this question from John.

Are you supposed to cut spent flowers on Encore Roses? Some say you are and others say don’t. Which is correct?

Cutting spent flowers is referred to as dead heading. Dead heading is like a minor form of pruning. People do it to most perennial flowers so that the plants look neater and it forces more flowering.

However, that being said, the Knock Out Roses are bred for easy maintenance and one of the things they have eliminated is making it necessary to deadhead. On their website it says “All seven members in The Knock Out® Family of Roses are self-cleaning so there is no need to deadhead.”

So though it is not necessary to deadhead spent roses from my Knock Out Roses, TheGardenLady will cut off the remains of the stem end of the roses that have died, but only for aesthetic reasons.

If you’d like to read a previous post on the issue of dead-heading Knock Out Roses, check this post out.

Getting Pricked by a Rose Thorn

Serious rose thorns by Martin LaBar

TheGardenLady received this question from Donna:

My sister-in-law was stuck by a thorn from a Knock Out Rose. The area is very red and swollen. Are the thorns poisonous? What to do?

When gardening, it is always advisable to USE gloves.

One can get an infection from any cut. However, in all the reading and lectures on plants, TheGardenLady has never heard that rose thorns in Knock Out Roses or any other roses are poisonous. But rose thorns can give a nasty cut. Because one can get cut when out in the garden and any cut can become infected, it is best to do any type of gardening – even cutting flowers – with gardening gloves on. And then after gardening you should always wash your hands. See here.

Besides cuts, thorns can give what are called “puncture wounds.” A puncture wound goes deeper into the skin and can push dirt and bacteria into the skin. Because it’s not on the surface and not an open cut, washing doesn’t clean out the wound as well, so it can become infected more easily.  As well, when you’re gardening outside, you’re exposed to all the dirt and bacteria out in nature, so there’s a wide range of what could be causing an infection.  Read this.

If an area is still red and swollen after getting a cut, one should consult a physician. Tell the physician how the area became infected so that one can get the best treatment to remove the infection.

More Questions About Knockout Roses

Red Knockout Rose by photomason
Red Knockout Rose by photomason

TheGardenLady recevied these additional questions about Knockout roses.

I just heard about the knockout rose and think it will be perfect for my side patio. Two questions: The above picture? are those purple or pink? How does the Knockout do in partial shade?

There is no purple Knockout rose. They have single and double pink, single and double red, and have recently brought out a yellow rose plus they have a rainbow colored rose and a pale pink single rose. Check out their site.

TheGardenLady has the pink and the red Knockout roses . Though the company says they grow 3 to 4 ft high and 3 to 4 ft wide, mine are higher – 5 or 6 ft tall and and about 5ft wide. I pruned mine down this spring yet they grew back as tall. They bloomed their heads off this spring. And with all the rain we have had, the plants are very healthy with no rose diseases.

I just had the lower branches of trees pruned so that the roses would get more sunlight. Until then they were getting about 5 hours of morning sun. But the company says they can do well with as little as 4 hours of sunlight.

If you’re interested in reading about blooming problems with Knockout roses, please take a look at this post.

Blooming Problems With Knock Out Roses

Gotta love those knock-outs!!! by perennialpal
Gotta love those knock-outs!!! by perennialpal

TheGardenLady received these two questions about Knock Out roses from Mary and Diane respectively.

I planted eight knock out roses in the sun last year and they bloomed. After blooming the first year I put mulch on the base of the rose bush and the ground was not frozen. This spring I cut them back slightly the first bloom was great. We went on vacation and had a bad rain storm and the roses stopped. What am I doing wrong?

Last Spring (2008) I planted 9 knock-out roses. They grew and bloomed fairly uniformly. This Spring they looked very healthy, and all burst into bloom at the same time. After the first bloom, two of them turned a very light green.  I have checked them for over/under watering. Fertilizing is not an issue as I have fertilized them all uniformly. The other 7 are beginning to bloom for the second time, but these two do not have new buds. They do not look like they are ready to die.  I can find no evidence of insect damage either at the root or leaf level. They are all planted in the same bed in one grouping for concentrated color (i.e. within feet of each other).  I am stumped as to what to do. Any ideas?

TheGardenLady imagines that you must have a fantastic show of concentrated color with those beds Knock Out Roses. TheGardenLady has just two Knock Out Roses and the floral show is amazing.

Two questions that are similar but not the same; however the treatment of the roses should be the same.

The first lady had Knock Out roses that stopped blooming after heavy rains knocked off the flowers and haven’t started reblooming.

The second lady has some of her Knock Out roses in one bed that are not blooming.

Continue reading “Blooming Problems With Knock Out Roses”

Soil for Knockout Roses

TheGardenLady received this question from Pat:

I am getting ready to plant Knockout Roses in my garden in northern South Carolina, and wonder how to best prepare the soil? We have very dense red clay mixed with some sand. Any recommendations on how to get these roses off to their best start in this type of soil?

Sorry it took so long to get back to you with a response, but TheGardenLady went right to one the sources of KnockOut Roses (see here) to get you the answer. I added a link to Permatill, a product mentioned in this column.

Here is the advice from a spokesperson for Novalis Plants that Work:

Continue reading “Soil for Knockout Roses”

Pruning Knock Out Roses


TheGardenLady received the following question from Pat:

I have Knockout Roses that are not yet a year old – They were planted last April – They grew very fast and produced beautiful flowers all summer long and into winter – I want to know do I cut them back and if so, when, and how short do I do this – They are getting ready to start blooming again, so I really need to know quickly the answer to my questions? I live in south central Louisiana

This is the answer given by Sally Credille, a PR person from Novalis Plants that Work, a licensed grower of Pink Double Knock Out and other Knock Out Roses:

“When it comes to recommendations and suggestions for care of Knock Out roses most include comments about their ease of care and low-maintenance. I cannot speak for all Knock Out rose varieties, but it is likely that general rose care is best for these landscape shrub roses, as with any others like it. This is because they were all bred by the same man, Bill Radler, for their hardy, low – maintenance, disease – and pest-resistance attributes.

Continue reading “Pruning Knock Out Roses”