Knockout Roses Bloomed Only Once

Filed Under: Roses · Keywords: Rose, Plant, Plants, Five, Up, Rose Bush, Hi, May, June, Health, New, Grow, Form, April, Started, Prune, Garden, Gardening, My · 2935 Views
I have six knockout rose bushes, five a one group and one lone bush. They were planted in 2010, and have provide a joy of profuse red blooms throughout the seasons until 2014. This year, we had one glorious crop of blooms in early May, lasting until mid June, but after they died off and I deadheaded as usual, NOTHING since. The plants are obviously healthy, covered with nice dark green leaves, but none even show the hint of a bud.

Around 10 days ago, a new stem began to grow off the lower part of an existing stem on one of the bushed in the 5-bus group, and it has clear signs of buds forming. The rest is just leaves. The lone bush decided to start forming buds and one bloom already. This is all puzzling, as although we had two extra-cold winters (2013-14 and 2014-15), the bushes sprang back in April and started showing leaves, and te lone bush that seems to beginning to bloom again, is out in the open where the winter wind - one would have expected - would affect it more, compared to the group of five which is more sheltered.

I have just read that I should have pruned all the bushed heavily in the spring. Being a gardening dummy, I didn't know I was supposed to do this. It never seemed to make any difference in previous years.

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Answer #4 ·'s Answer · It's a good thing your Knock Out Roses look healthy. They do go through bloom cycles...usually three to five per year, depending on weather. I've noticed that mine aren't blooming as heavy as they have in the past...but neither are my hydrangeas, crape myrtles and other flowering shrubs. I'm thinking it could be weather-related. Maybe a combination of the unusually cold temperatures during the past two winters and the hot summer temperatures we're having now. That being said, I think some heavy pruning next late winter might help to rejuvenate the plants and encourage new branching that might produce more buds. We've had a lot of rain over the past two years here in mid-Goergia that has probably leached a lot of nutrients from the soil, so an application of triple superphosphate and an organic plant food, such as Milorganite or NITROGANIC, might be helpful as well to rejuvenate plants.

Keep us posted as to how your roses do and I'll provide an update on mine as well.

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Answer #3 · Maple Tree's Answer · Nick-I believe the problem of reblooming has mostly to do with the pruning of your Knock Out Roses. From what I know the first two or three years are not as important when it comes to pruning as the plant needs time to develop a good root system and stem structure. A young Knock Out Rose will most likely produce enough new branching to bloom fine. As the Knock Out Rose matures pruning is the most important thing you can do for your Knock Out Roses to stay healthy and produce abundant blooms. Older canes will become less productive and is why they need pruning back. The pruning back in late winter or early spring encourages new lower shoots which is essential for any rose to stay blooming well. These new shoots like the one you have appearing on the one rose is needed to keep your roses healthy with continued new growth. These new shoot will be just above the graft and much more productive than the old growth. These lower shoots above the graft are what you want. Any shoot coming from the rootstock or below the graft are sucker shoots and should always be removed.

Why one plant does better than another can be hard to determine at times. There are many factors that play a part in why one plant does better than another. Temperatures, soil, nutrients, and amount of sunlight all play a part in a plants health and growth characteristics. The amount dormancy time and temperatures can also determine the health and growth of many plants. Possibly the one rose more exposed to colder temperatures had a more beneficial dormancy than the others that were more protected. As a collector of Japanese maples and some conifers I have seen the affect lower temperatures for a needed period of time, producing beneficial dormancy, have on the health of a plant regarding their foliage and flower production. All roses need a dormant period to rest and build their resources for next years flush of new foliage and blooms.

Again, it sounds as though your roses are growing well and healthy. The last 5 years pretty much attests to this. I don't believe unusually cold temperatures have affected these plants as they supposedly leafed out and bloomed well in the spring with no indication of winter damage. Any yellowing or spotting of the leaves would be an indication of possibly too much water from all the rains you have had but this doesn't seem to be a problem you have seen. These roses need a lot of direct sunlight to bloom well. With one of the plants blooming well now I'm assuming cloudy weather with little direct sunlight isn't the problem. I believe the plants now older have stems that are becoming less productive. I think with a little patience this year you may still see some blooming during the summer. Pruning next spring will most likely make a difference in the production of new shoots producing more blooming. If you have fertilized with a fertilizer formulated for roses they should have the nutrients they need. Fertilizes with a higher percentage of phosphorus, the second number in the formulation, will help with the production of blooms. You might also try pruning any of the roses that aren't showing buds in order to promote more blooming. You can prune back these plants by 1/3 any time of year but no later than 2 months prior to the first frost.

Let me know how these roses are doing during the year.


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Answer #1 · Maple Tree's Answer · Hi Nick-Knock Out Roses should be pruned back each year before new growth appears. The new growth each year will keep the plants healthy and produce several bloom cycles during their growing season. Possibly the older stems are not as productive as the newer growth would have been if pruned back. Although the last couple of years unusual weather has changed many plants growth habits your plant's developing nice green growth this spring is an indication they are most likely healthy.
The Knock Out Roses have a bloom cycle about every 5 to 6 weeks. A few things can stop or make bloom times further apart. Hot temperatures can slow bud development. If you have had temperatures in the ninties this may have slowed bud development. The amount of sunlight will also be a factor in how well your Knock Out Roses will bloom and when. These rosed need as much direct sunlight as possible to bloom well. If you have had a lot of cloudy days this may have affected the development of buds and blooming. A lot of locations have had a lot of rain this year causing many to not water as often. These roses appreciate a moist soil but not one that is too wet or dry. If your foliage is a nice green and not yellowing they most likely are not getting too much water. Make sure the plants are deeply watered in order to moisten the entire root ball to their depth. Too little water can also stop flower bud development. Have these roses been fertilized and if so with what fertilizer? Ferilizers especial formulated for roses should always be used. Many fertilizers especially those used for lawns have too high a nitrogen content. Too much nitrogen will help to develop a lot of green new growth at the expense of flowers. Are these roses possibly planted near an area where lawn or other plants have been fertilized? Possibly leaching of fertilizer from other areas into this location may have happened.

The Knock Out Roses are self cleaning so there is no need to deadhead them unless you want to keep them looking a little cleaner. Some light pruning after whatever first blooming they had may help encourage your plants to bloom again. With the plant's foliage looking nice, no discoloration of the leaves, no appearance of insect damage, with some buds forming I would assume it may just take a little more patience this year to see another bloom cycle.

Let me know if you think any of these reasons may be why the plants are not blooming. Also, please ask if you have any other questions. You definitely are no gardening dummy. We were all new to gardening at one time or another. If we ever think we know all there is regarding the proper care of all plants we are wrong. Gardening and landscaping is extremely exciting and rewarding for me as I am always learning new things from others and the trials and errors I have made with the growing of my plants. Websters definition of a Dummy is a stupid person who is habitually silent. That is definitely not us as I believe the saying, "A stupid question is the question that is not asked". The knowledge I have gained through the years regarding gardening has unfortunately included many failures.


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Answer #5 · Nick Odell's Answer · Many thanks again for taking the time and providing such comprehensive information.

I've pruned the existing foliage back about 25 - 30% and taken off some dead canes from last year I must have missed before. The "lone ranger" bush is producing a lot of great blooms right now, and my major problem here is constantly checking for ......

"She rove you, yeah yeah yeah, she rove you, yeah yeah yeah, with a rove rike this .... etc." (Japanese Beatles.)


I'll keep you up to date re. the progress of the group of (Dave Clark) Five bushes.

Sorry again. I'm a transplanted Brit; we can't help ourselves.)

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Maple Tree

Maple Tree · Gardenality Genius · Zone 10A · 30° to 35° F
You're very welcome. Definitely keep us up to date, you and Brent both as this can always help others also with the same problem. Boy do those lyrics bring back memories of the year I graduated high school. Oops, I just dated myself. Take Care

8 years ago ·
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Answer #2 · Nick Odell's Answer · Dear John,
Thanks for taking the time with such a detailed reply. The bushes were all fertilized when they were in bloom, using a specific rose fertilizer, which was well watered into the roots. We have had a lot of rain this spring and early summer (so much that I have not had to water my lawns once!) Three things puzzle me:

1) In the five previous years, blooms appeared in the spring and continued well past the first frosts; these are hardy plants! Nothing has changed this year regarding watering, fertilizing etc., and temperatures have for the most part been mild this summer, averaging 70s and 80s during the days and 50s or 60s at night (we are in SE Pennsylvania) - so what caused the sudden cessation of blooming? I understand your note about the 5 or 6 week blooming cycle, but in previous years these cycles have overlapped so that there were always plenty of blooms all summer and fall; never a total end with zero signs of new bud formation.
2) What's with the single new stem originating low down from an existing stem in one of the 5-group bushes, and rising up with buds evident and appearing ready to bloom in a week? Why not buds and blooms on the existing stems?
3) Why is the lone bush, out in the middle of the lawn and exposed far more to the last two winters' icy blasts (as low as zero F) now producing multiple buds and some blooms.)

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