Decado
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Rhododendron In Fall

What is this supposed to do in terms of color change? Mine looks like most the leaves are getting darker, but I also have all yellow leaves about 6 inches from the bottom. I thought rhododendron was part evergreen, is it supposed to change colors like this or am I having some kind of problem? FYI, I just planted it this year.

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Kisal
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Rhodies are called broad-leafed evergreens. They retain their leaves and green color all year round. The healthy leaves don't change color. However, leaves do eventually die, turn yellow, and fall off, but a rhodie shouldn't lose more than a few each year.

As the plant grows, many of the leaves from the interior of the plant may die, depending on whether the branch structure is properly pruned to admit sufficient light.

Improper growing conditions, such as too much or too little water, compacted or poorly drained soil, not enough or too much light, and improper soil pH can cause leaves to drop, as well.

There are some insects that will attack the leaves ... the rhododendron root weevil comes to mind. They tend to attack the lower leaves, and could possibly cause them to yellow. The most common damage by that insect is chewed leaf edges.

Perhaps you could post a picture of your plant? I think that might be helpful to members who might be able to offer advice. :)

Decado
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[img]https://i3.photobucket.com/albums/y69/wrathloki/Rhododendron-01.jpg[/img]

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Kisal
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I can't be sure, but it almost looks to me as though whatever caused the problem occurred earlier in the year. The newer growth looks good.

Did the yellowing occur recently and suddenly?

It impresses me as maybe being a water issue, whether too much or not enough is hard to say, though. Either could lead to root damage. Could it have been overwatered during the month or so right after it was planted?

The only other thing I know of that might cause that kind of yellowing of leaves lower on the branches would be a problem with soil chemistry. You may want to test the pH of the soil, to make sure it's acidic enough. (You can buy a soil testing kit at most plant nurseries and garden stores. I've even see them at some of the big-box stores. In some areas, the Extension Service will do simple soil testing for free or for a nominal fee.) If the soil pH isn't right, the plant won't be able to access the nutrients it needs, even if they are plentiful in the soil. I can't see the leaves clearly enough to make a determination from the picture, but it looks as though some of them have a slight greenish cast. I suggest you examine them firsthand, looking for yellow leaves with green veins, which would be evidence of chlorosis, and a common symptom of improper soil pH. Just a suggestion.

If you have an Extension Service office in your area, you might want to cut a section of branch with both yellow leaves and healthy green leaves, and take it in to show to one of their Master Gardeners. There's always the possibility that there is some bacterial or fungal infection present that I simply can't see in the photo.

Decado
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Kisal wrote:I can't be sure, but it almost looks to me as though whatever caused the problem occurred earlier in the year. The newer growth looks good.

Did the yellowing occur recently and suddenly?

It impresses me as maybe being a water issue, whether too much or not enough is hard to say, though. Either could lead to root damage. Could it have been overwatered during the month or so right after it was planted?

The only other thing I know of that might cause that kind of yellowing of leaves lower on the branches would be a problem with soil chemistry. You may want to test the pH of the soil, to make sure it's acidic enough. (You can buy a soil testing kit at most plant nurseries and garden stores. I've even see them at some of the big-box stores. In some areas, the Extension Service will do simple soil testing for free or for a nominal fee.) If the soil pH isn't right, the plant won't be able to access the nutrients it needs, even if they are plentiful in the soil. I can't see the leaves clearly enough to make a determination from the picture, but it looks as though some of them have a slight greenish cast. I suggest you examine them firsthand, looking for yellow leaves with green veins, which would be evidence of chlorosis, and a common symptom of improper soil pH. Just a suggestion.

If you have an Extension Service office in your area, you might want to cut a section of branch with both yellow leaves and healthy green leaves, and take it in to show to one of their Master Gardeners. There's always the possibility that there is some bacterial or fungal infection present that I simply can't see in the photo.
I looked at the full size image and there's definitely green veins on those yellow leaves.

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Kisal
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Okay. Then definitely, the first step would be to test the soil pH. As I mentioned, you can buy a soil test kit, or you can send out a soil sample to have it done professionally. I have used soil test kits and found them to be fairly simple and straightforward. You could call your nearest Extension Service office to learn whether they offer free soil testing, or whether they charge for it. You may find the charge to be less than the cost of a kit.

Chlorosis develops when a plant cannot absorb sufficient nutrients from the soil because it is either too acid or too alkaline. There may be plenty of the nutrient available in the soil, but the plant just can't absorb it. Rhodies like acid soil, and if the pH of your soil does fall in the acidic range, then you'll need to measure the levels of nitrogen, phosphorus and potassium, and add amendments to adjust whatever is lacking.

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rainbowgardener
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Rhododendrons are definitely acid lovers, require acid soil. Some plants prefer acid soil, but will still grow in more neutral, but rhododendrons just up and die if the soil isn't acid enough for their taste. They want soil pH down around 5.



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