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New to Rhody's...help with yellowing leaves..

Posted by its_alive z8 Oregon (My Page) on
Sun, Apr 30, 06 at 8:51

Hi everyone,

I am very new to growing Rhody's. I have one that is looking very sickly. The leaves are not a nice dark green, they are pale and yellowing.

The plant was given to me, and I would hate to loose it. What I know about this plant, the person has it for years, and it was a wild rhody when they had got it. It was beautiful when I gotten it.

Is the plant lacking something? It had a nice root ball when I planted it, also could it be getting to much sun? Where I have it planted, it get sun about 3/4 of the day, until late afternoon.

Any and all information would be wonderful.
Thank you all for your time.


Follow-Up Postings:

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RE: New to Rhody's...help with yellowing leaves..

  • Posted by morz8 Z8 Wa coast (My Page) on
    Sun, Apr 30, 06 at 12:25

Your normal soil ph should be fine for rhododendrons unless something has been done to alter it...addition of lime, brick wall, new patio poured nearby.

If we assume it isn't the ph of your soil, other reasons for the rhododendron failing could be planting too deeply...these have a dense network of surface roots that can't function when buried too deep. Overfertilization can kill enough roots that the remainder are unable to provide nutrients to the top growth, and poor drainage (we had a lot of rain this year) - does your ground stay soggy where you've sited this plant, is it in a low spot or near a downspout?


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RE: New to Rhody's...help with yellowing PS

  • Posted by morz8 Z8 Wa coast (My Page) on
    Sun, Apr 30, 06 at 14:15

Woops, that was supposed to have a link to rhododendron culture local to you :(

Here is a link that might be useful: Rhododendrons Portland Chapter


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RE: New to Rhody's...help with yellowing leaves..

It could be getting too much sun, in general they grow like weeds here depending on where in Oregon you are.

The native ones grow in forests, not in full sun. I have found they don't transplant well. That may be the problem.


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RE: New to Rhody's...help with yellowing leaves..

Thanks for your replies.

I am in Eugene. This plant was in the wild some years ago. ( so it wasn't like it was just dug up out in the forest. )
It could be getting to much sun where I have it.

Do you think if I moved it to another area, it would be okay?

The area where I have it planted now, the ground is level, and it doesn't stay soggy. I haven't fertilize it yet. How does one go about checking the Ph of there soil? What type of fertilizer should I use?

Thanks again!
Cheryl


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RE: New to Rhody's...help with yellowing leaves..

Yellowing of leaves has many causes. Here are some causes:

Yellowing of a leaf between dark green veins is called chlorosis. Many conditions can be responsible. Poor drainage, planting too deeply, heavy soil with poor aeration, insect or fungus damage in the root zone and lack of moisture all induce chlorosis. After these conditions are eliminated as possible causes, soil testing is in order. Chlorosis can be caused by malnutrition caused by alkalinity of the soil, potassium deficiency, calcium deficiency, iron deficiency or magnesium deficiency. A combination of acidification with sulfur and iron supplements such as chelated iron or iron sulfate will usually treat this problem. Chlorosis can also be caused by nitrogen toxicity (usually caused by nitrate fertilizers) or other conditions that damage the roots such as root rot, severe cutting of the roots, root weevils or root death caused by extreme amounts of fertilizer.

Small white spots on the underside of leaves and small white flies on under-surface of leaves may indicate in infestation of whitefly. These small white flying insects look like an aphid with wings and suck on the underside of foliage, leaving white spots where it has been. To control use Malathion, Diazinon or Orthene.

Yellow mottling on the upper surface of leaves and black sooty mold and transparent insects on the bottom are symptoms of whitefly also. They are more prevalent on certain varieties and on plants grown in protected areas. When damage first appears, it may be controlled by any of a number of contact insecticides. Care must be taken to spray the lower surfaces of the leaves where the whitefly live.

Yellowing of leaves surfaces, often with brownish burned areas, occurring on leave that are more exposed to sun, is caused by more sun exposure than the plant is able to tolerate. Some varieties need shade, while all plants that have been protected from direct sun will be tender until hardened off by gradual exposure to sun light. Possible solutions are to give the plant more shade or move it to a more protected site.

Yellowing and dropping of leaves is normal toward the end of the second summer on the small-leaved lepidote rhododendrons. These should have dense enough habit that this doesn't matter. The larger-leaved elepidote rhododendrons keep their leaves for 3 or 4 seasons.

Uniformly yellowish-green leaves is often just the need for more nitrogen. This will be more noticeable in the full sun. Some less sun tolerant varieties will always be light green in full sun.

Yellowing of leaf edges has been noted in gardens where sandy soil conditions or root competition with other plants caused insufficient soil moisture and nutrients. Usually incorporating organic material in the soil and removing the plants with the competing roots solved the problem. Care must be taken not to disturb the roots of the rhododendrons and azaleas. Hence it is best to prepare the soil adequately before planting. The tops of most competing plants can be removed leaving the offending roots in the ground and the offending roots will simply decay and pose no problem.


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RE: New to Rhody's...help with yellowing leaves..

  • Posted by morz8 Z8 Wa coast (My Page) on
    Sun, Apr 30, 06 at 19:00

Your PH in Eugene soils, if nothing has been done to alter the natural acidity, should be perfect for rhododendrons.
I never fertilize mine, but I top dress with compost in Spring, sometimes adding more in Fall.

If I were new to rhododendrons and living in Eugene, I would take a pretty Spring morning, drive out to Greer Gardens, 1280 Goodpasture Island Rd, browse around and learn all I might ever need to know about these shrubs.


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RE: New to Rhody's...help with yellowing leaves..

Rhodyman and Morz,

Thank you both for all this information. You both have been wonderful!

I am going to move this rhody this weekend, to a area that get more shade. I found a nursery here , that would test my soil for me. I had to haul in few truck loads of good compost for my veggie garden, so I could grow a better crop this year. My soil is sorta like sandy mix with clay ( I guess it's clay ..lol )I have never seen dirt like this before.. when it dries , it gets really rock hard.

Thank you both again , helping a newbie to rhody's.
Cheryl


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RE: New to Rhody's...help with yellowing leaves..

Yes, it is clay and most likely acidic.

I mentioned the native Rhodies not liking transplanting because you said it had just been given to you and I thought you had just planted it. I didn't mean that it had just been dug up from the wild. :)

Definately give it some more shade. I would not fertilize it. Maybe topdress with compost. I have almost twenty Rhodies and I don't ever fertilize here.

When you transplant it, don't plant it deep, you want it raised a bit and then mulched on top.

I second the advice to visit Greer Gardens.


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RE: New to Rhody's...help with yellowing leaves..

I have 2 rhodies in our gardens. One is a pink one ("Roseum"? commonly available almost anywhere), the other is Nova Zembla. I'm posting here following a search and some very interesting reading, that has left me scratching my head. (have never done a soil test, but Astilbes, Aruncus, Epimedium, and Osmundas grow beautifully, in addition to woodland ephemeral bulbs).

My plants' leaves have taken on a decidedly "olive" green appearance over the years (pink one is nearly 10, Nova is 6). They are in partially shaded locations, weren't planted too deeply, and have flowered reliably every single year, in addition to putting on growth. They're budded up nicely right now and typically flower in mid/late June. I wonder if their color might be related to moisture level? but they certainly don't sit in heavy soil.

Does the leaf color described sound as though they might like a shot of Nitrogen? I'm confused about this and how I ought to go about accomplishing it as we're coming into flowering. Should I simply sprinkle some compost over the root area and leave this until next early spring?

As it stands, they look quite healthy and they will flower, I am not concerned about their survival. But they don't have that luscious deep green foliage I see on plants at the nursery.


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RE: New to Rhody's...help with yellowing leaves..

My Rhody has also developed yellow leaves, its about 30 years old and it was moved to my house about two years ago, six weeks ago I fertilized it with holly tone, what could be the cause of this?


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RE: New to Rhody's...help with yellowing leaves..

Hollytone is the best fertilizer for plants like rhododendrons, but should only be used once a year if at all and then only at half the rate on the package. More is not better. The nitrogen (N) is organic and fairly harmless. The phosphate (P) is good. But the potassium (K) can be too strong and cause problems. For example, cocoa shells have a high potassium content that injures plants such as maples, lilacs, rhododendrons, and azaleas.

Since rhododendrons have very shallow roots, you can only sprinkle fertilizer on the ground, preferably under the mulch and wait for it to work its way into the soil. Actually in many circumstances, the roots work their way into the mulch. Never cultivate the soil under a rhododendron, you will damage the roots.

Some yellow leaves near the inside and bottom are normal. The leaves don't live forever. They die after a couple years.

A nitrogen deficiency will cause a uniform yellowing of all leaves. Hollytone should prevent that.

If the leaves are yellowing between green veins, then the plant is chlorotic. Since you applied Hollytone, I doubt if it is chlorotic, but if it is then:

Yellowing of a leaf between dark green veins is called chlorosis and is usually caused by an iron deficiency. Many conditions can be responsible for an iron deficiency. Poor drainage, planting too deeply, heavy soil with poor aeration, insect or fungus damage in the root zone and lack of moisture all induce chlorosis. After these conditions are eliminated as possible causes, soil testing is in order. Chlorosis can be caused by malnutrition caused by alkalinity of the soil, potassium deficiency, calcium deficiency, iron deficiency, magnesium deficiency or too much phosphorus in the soil. Iron is most readily available in acidic soils between pH 4.5-6.0. When the soil pH is above 6.5, iron may be present in adequate amounts, but is in an unusable form, due to an excessive amount of calcium carbonate. This can occur when plants are placed too close to cement foundations or walkways. Soil amendments that acidify the soil, such as iron sulfate or sulfur, are the best long term solution. For a quick but only temporary improvement in the appearance of the foliage, ferrous sulfate can be dissolved in water (1 ounce in 2 gallons of water) and sprinkled on the foliage. Some garden centers sell chelated iron, which provides the same results. Follow the label recommendations for mixing and applying chelated iron. A combination of acidification with sulfur and iron supplements such as chelated iron or iron sulfate will usually treat this problem. Chlorosis caused by magnesium deficiency is initially the same as iron, but progresses to form reddish purple blotches and marginal leaf necrosis (browning of leaf edges). Epsom salts are a good source of supplemental magnesium. Chlorosis can also be caused by nitrogen toxicity (usually caused by nitrate fertilizers) or other conditions that damage the roots such as root rot, severe cutting of the roots, root weevils or root death caused by extreme amounts of fertilizer. There is a tonic that remedies some cases of chlorosis.

Chlorotic Leaves

Here is a link that might be useful: Rhododendron and Azalea Problems


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RE: New to Rhody's...help with yellowing leaves..

I f soil Ph is good sometimes i add a little Ironite and they green right up.But if you are going to use it get the kind that has only 1% nitrogen,it has everything else including Magnesium sulfate and sulpher. Joe


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