Knowledgebase
Why are my roses turning brown from the bottom #872434
Asked June 10, 2024, 1:56 PM EDT
Can you tell me what's going on with my rose bushes? They have healthy, blooming tops but the bottom of the bushes are turning brown. There are still some green stems and 'healthy' blooms even though the leaves are dead. The leaves do not have holes in them like they are being eaten. There are no visible webs or bugs that I can see. There appears to be no dust, powder or residue or anything that would resemble a spore. These are well established bushes for the last 24 years. I give them a bucket of water with Miracle Grow rose food every other week. The only other water they get is what mother nature provides. This has been the same for the last 24 years.
Weld County Colorado
Expert Response
This is indeed puzzling, Ms. Inouye!
Let’s explore some possible reasons for what you are seeing.
*Are all of your roses affected?
*When did you first notice these symptoms?
*What are the plant site conditions? Have there been any changes during the past year or two?
*What do you see at the rootstock junctions?
*Do you see anything unusual when using a hand lens?
*Any collection of debris around the plants during the past 12 months?
*Was there nearby herbicide application during the past 12 months?
* What may have changed in the area of your roses? New mulch? How deep is mulch?
* Are you using a new batch of rose food? Has the formulation of rose food changed from what you used previously?
*What do you think might be the cause of the problem?
I hope we can get to the bottom of this soon.
Sue, Weld County Colorado Master Gardener
Right now I'm looking at this CSU bulletin:
https://cmg.extension.colostate.edu/Gardennotes/223.pdf
I have contacted the CSU Extension rose expert and showed him your photos.
As soon as I hear back from him, I'll get in touch with you.
Sue
Weld County Colorado Master Gardener
Ms. Inouye,
Our Extension rose expert believes you have an easily fixable "too-little-water" problem.
He says roses can store water only so long and two weeks is too long, he says. One good deep watering once a week would be better. Perhaps you already have a wonderful bed of topsoil with a soil pH of 7.0 and 5 percent organic matter. Otherwise, he said, especially during hot weather, it’s best to check your plants’ water needs by taking a long screwdriver and poking it into the ground around a rose bush. Obviously, if the tool is wet and muddy when you pull it out, the soil is too wet. “If you have trouble getting the tool into the ground, the soil is too dry and needs watering,” he says, “ASAP.” Before you start watering, it would be best to remove and destroy all those brown, dried-up and dead leaves you see, especially at the base of your rose bushes.
The weather has been hot and that’s another stressor. Variable weather is also a stressor.
A third stressor he mentioned is fertilizer. The Denver Rose Society recommends a fertilization of slow-release organic fertilizer that has a ratio of 5-4-3. Note that this has a low phosphorus ratio. The timing of fertilizer application is once in late Spring, once in July, and one last time in September.
These suggestions differ slightly from the Colorado State University Extension’s Plant Talk publication #1725, Rose Maintenance: https://planttalk.colostate.edu/topics/trees-shrubs-vines/1725-roses-maintenance/
Roses that are under stress (water+weather+fertilizer) are subject to attack by aphids, caterpillars, grasshoppers, mites and thrips. Ugh!
I hope these suggestions help you enjoy your roses this summer.
If you have questions or other concerns, please do not hesitate to contact CSU Extension.
Sue, Weld County Colorado Master Gardener
