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I cant grow rhodys!!

Posted by hobbitmom z8pnw (My Page) on
Thu, Sep 7, 06 at 2:31

I live in the PNW, in a neighborhood that has an abundance of beautiful rhodys, but for some reason, they die on me. Ive tried about eight times, and followed all the rules, they would seem to have a textbook environment to thrive, but.. sadly, time and time again they slowly die. They die leaf by leaf. The individual leaf will droop and turn yellow, then brown, then fall. This is scattered throughout, not in a given area, but the result is the same over time, not good. I pamper the daylights out of them, I have also given them some Bayer all in one, in case it is a fungus. My current sick rhody is called "unique" but in my experience, it certainly is NOT. Anybody know whats going on here?? Other plants do fine. Thanks.


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RE: I cant grow rhodys!!

  • Posted by morz8 Z8 Wa coast (My Page) on
    Thu, Sep 7, 06 at 15:47

Too much pampering maybe?

You may feel you are following all the rules, but rhodys are fool proof enough here you must be missing one. So, basic requirements - don't plant too deeply, keep root ball at the same level or slightly higher than growing in the nursery pot. Loosen the rootball at installation time so the roots can reach out into the surrounding soil. Don't plant in an area of really bad drainage. Keep soil moist but not soggy, particularly the first year and if it's been a dry year like this one...mulch the root zone to conserve that moisture and cool roots.

Some leaf drop of the oldest, innermost leaves is normal. Skip the Bayer, or any other form of intervention, unless you have a specific symptom you are addressing....that includes fertilizer as these shrubs have low nutritional requirements compared to most.

You say these do great in your neighborhood but badly for you - could you be a little more specific about your site, soil type, time of year you've planted, planting steps you've taken? Once in the ground correctly, these are almost no care landscape shrubs (exceptions watering, deadheading) - There has to be an easy way to fix this :)


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RE: I cant grow rhodys!!

thank you for your responce,but I cant think of a single reason for my troubles. I follow the rules to a tee. For fear of drainage problems, I plant them in a raised bed made with good quality stuff, organic, on the light side. And I have thought that if it were a drainage problem, it wouldnt effect the leaves in such a scattered manner. maybe. I have not found any notched leaves, or anything like bugs. I used the Bayer as an experiment. (didnt help) This whole thing is quite annoying. Thanks again.


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RE: I cant grow rhodys!!

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. Like all evergreen plants, rhododendrons and azaleas periodically lose some of their foliage, and the leaves may turn yellow, red, or purple before they fall. Often the only leaves that remain are those that surround the flower buds at the tips of the branches. This characteristic is linked to the genetics of the parents used to breed garden rhododendrons and azaleas. The degree of leaf coloration or loss is a function of parentage and not the severity of the winter. In unusually cold winters, certain varieties may lose more leaves than they would in mild winters.

When all the leaves do this, it is signs of a problem.

1) The most common problem is too much water. They should not be watered until they show some signs of water stress such as some drooping of the leaves.

2) Another problem is when the roots get too hot from exposure to summer sun. This is avoided by having some shade and using a good mulch to keep the roots cool.

3) An third problem is root strangulation. This is best prevented by proper root pruning when planting. If the plant is not too far gone, it might be rescued by digging and removing the soil. Then cutting any circling roots that may be strangling other roots. The roots need to be opened up. On larger plants, some of the top must be removed to compensate for the weak state of the roots. Any time the roots are exposed, they must be kept moistened. Roots that dry out will die.

4) A 4th problem is drought. It may have simply dried out. If you plant rhododendrons or azaleas in late spring, it is very important to give them some extra water while they are growing new roots. Never let the soil completely dry out' it's best to keep the soil evenly moist. Too much water or poorly drained soil might be another explanation of rhododendron or azalea death. Rhododendrons and azaleas have very fine, fibrous roots that are easily damaged by waterlogging, even for short periods of time.

5) A 5th problem is voles. Voles, also known as meadow mice, may have chewed on the bark and roots near the crown of the plant. Sometimes they chew all the way around the trunk and kill the inner bark, resulting in death of the whole plant. Keep mulch away from the trunk to discourage voles.

6) Another problem is bark split. The bark may split when there are wide fluctuations in temperature in the winter. Rhododendrons and azaleas may begin to come out of dormancy if late winter weather is warm; if a cold snap follows, bark injury is likely, especially in sunny, exposed sites.

7) A final possibility is juglone poisoning. It is caused by toxins released by the roots of black walnuts and butternut trees. Persian (English or Carpathian) walnut trees are sometimes grafted onto black walnut rootstocks. The roots release a substance called juglone (5-hydroxy-alphanapthaquinone) which is very toxic to rhododendrons and azaleas.

Here is a link that might be useful: How to grow rhododendrons and azaleas.


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RE: I cant grow rhodys!!

Are you keeping an acid soil? If the soil is not acidic enough, the leaves can yellow and drop.


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RE: I cant grow rhodys!!

If the soil is not acidic enough, the rhododendrons develop iron deficiency which is characterized by yellow leaves with green veins. It is rather distinctive and is called chlorosis. 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 or magnesium deficiency. 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. Foliar sprays of iron sulfate or chelated iron can reduce symptoms. 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.

Here is a link that might be useful: How to grow rhododendrons and azaleas.


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RE: I cant grow rhodys!!

  • Posted by morz8 Z8 Wa coast (My Page) on
    Tue, Sep 26, 06 at 10:56

Bogie, our soil is naturally acidic enough, combined with ample amounts of mildly acidic rain, to easily sustain rhododendron unless changes have been made to the landscape to alter the acidity. i.e. areas of newly created cement, excessive liming of soil.


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RE: I cant grow rhodys!!

thank you all, the fallen leaves are yellow with brown spots (im unable to post a pic.) Thats why I tried Bayer 3 in one, thinking it looks like a fungus, maybe.


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RE: I cant grow rhodys!!

It could be Phomopsis rhododendri. Symptoms vary from leaf spots to chlorosis (yellowing) and then browning of leaves which then wilt. Browning streaks extend down the stem to a wound. Fungicides such as metalaxyl (Subdue) should control an outbreak. Sanitation and applying a fungicide after pruning may provide control.


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RE: I cant grow rhodys!!

Rhodyman, I couldn't follow your train of thought, browning of the leaves, not the whole leaf, just a partial on the leaf is magnesium deficiency and the azalea needs some epsom salts? I was going to get some iron sulfate. I have total alkline soil, didn't realize when I planted all 3 azaleas. One is doing better than 2, One gets more shade. The other 2 will next summer when the austrailian tree fern gets it's 10 foot height I planted to shade it. Someone told me to mist it, it's getting to hot. Your description of the browning of the leaves says magnesium deficiency. Leslie


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RE: I cant grow rhodys!!

Leslie,
First you need to adjust the pH. Rhododendrons and azaleas need an acid soil with a pH of 5.0 to 6.0, well mulched with organic material. Have a soil test done by your local extension service to determine if something needs to be added. If the soil is too alkaline, acidity may be increased by adding flowers of sulfur (powdered sulfur) or iron sulfate. For the rate of sulfur to apply check:

Pounds of elemental sulfur needed to lower soil pH of a silt loam soil to a depth of 6 inches.

An alkaline soil will cause iron and magnesium deficiencies even if these minerals are there. Adding epsom salts (Magnesium Sulfate) won't help if the pH is too high.
Alkalinity of the soil can cause potassium deficiency, calcium deficiency, iron deficiency and magnesium deficiency.


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RE: I cant grow rhodys!!

oops, I went down and got iron sulfur and granulated sulfur and posted a thread on the soil forum about what's the difference. I also was going to "plop" in some epsom salts for good measure.... Guess not. When do azaleas rest anyways? When should I mess with them? They are putting new growth out, browning on the leaf edges is only occuring on the old lower growth. Thanks for answering me. Guess I shouldn't have planted in July. It was 90 when I did and hit 117 as a high. My soil ph is 8 by the way. Leslie


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RE: I cant grow rhodys!!

Since you just planted these and you planted the root ball and soil that came with them, they still have the residual acidity from that soil. The roots won't be able to expand into the alkaline soil. My recommendation would be to pull them out, make a raised bed with soil of the correct pH and then replant them in the raised bed. It is a loosing battle to try to adjust the pH of the native soil when it is that alkaline. I am sure that there is a lot of literature about raised beds in your area. You can adjust the pH in a raised bed much easier than in the native soil.

When preparing new raised beds in soil that is not acidic, the pH may be lowered by adding flowers of sulfur (powdered sulfur). Amounts of powdered sulfur needed to lower the pH of a silt loam soil to a 6-inch depth are given in the table above. A target pH of 5.5 is ideal for most rhododendrons and azaleas. Sandy soils would require less and clay soils would require more. Elemental sulfur is converted to sulfuric acid by soil bacteria. Therefore, in order for sulfur to work the following must be satisfied:

* Sulfur must be mixed with the soil to provide contact.
* The soil must be moist
* The soil must be aerated (bacteria need oxygen).
* The soil must be warm for rapid bacterial growth.
* Time is required for the reaction to go to completion.

Obviously it would be best to use an acidic soil rather than try to adjust an alkaline soil in the raised bed. However, if you don't have access to any acidic soil, then you would have to play the pH adjusting game in the raised bed. The advantage is that you can mix the materials uniformly with the soil.

In your case I would put some kind of a barrier between the raised bed and the native soil. This could be a layer of gravel. That would prevent water from going up and would still provide drainage.

Here is a link that might be useful: How to grow rhododendrons and azaleas.


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RE: I cant grow rhodys!!

Thanks I appreciate it, one last question, when is the best time to do it, they're flowering now? Or in the winter? I've got them right against the house. I do appreciate your time. I'm going to print your answers and check your link. Leslie


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RE: I cant grow rhodys!!

They can be transplanted any time. If their health is going down hill, the sooner is better. If they seem to be maintaining their health, then it would be best to wait until after they bloom and go dormant. I have never raised azaleas in southern California, but I am surprised they are blooming now. They are normally spring blooming plants. They should go dormant for the winter if you have one. I know San Diego has a very stable mild climate all year long.


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RE: I cant grow rhodys!!

In fact I have Ultimate Pink and Freckles blooming, Happy Days is not, it doesn't give a plant brand for some reason I'm thinking they're southern indica however the 1st and 3rd bushes are similar and Freckles is a taller bush. Freckles' bloom is just that, freckled, is a hardier bush and is really pushing up new green growth at the top and sides that doesn't have any brown at all. Ultimate Pink in a different front flower bed gets a different amount sun is putting out new green growth without brown. Happy Days has a new small amount of green growth without brown and is kind of sullen. This one I'm most worried about and hasn't flowered. I am in the central valley of CA closer to Bakersfield and Fresno than San Diego. I don't have very many blooms but the two do have blooms. I thought they were spring blooming also, at the rental I was in they bloomed in spring also. I'll wait then and let them go dormant until late winter. Thanks, I appreciate your input and knowledge. Leslie


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RE: I cant grow rhodys!!

You almost certainly have one or more diseases. Rhododendrons are extremely easy to grow here except for fungal diseases, which have gotten worse in recent years. Rhododendrons like all members of Ericaceae are extremely susceptible to a number of fungal diseases. My yard for example is full of Phytophthera (despite the fact that my soil is like beach sand), which will kill a Rhody in a few days or weeks.

DO NOT WATER OVERHEAD. It spreads the spores. Try a "leaky hose" type watering system, or a microirrigation system.

Make sure drainage is good, make sure the Rhodies are above the lowest point in your yard. Try to disturb the soil as little as possible, and use mulches. They seem to help.

You might consider trying a product called "Root Shield". It consists of spores of ANOTHER fungus, which is harmless to plants and competes with the deadly fungii. Another product that might help is a fungucidal bacterium. I am using both products, plus sulfur.

You might try taking the leaves to a master gardner to see if they recognize the specific symptoms. A "V-shaped" dead zone on the leaf is Phyto (speaking from experience). It kills the leaves, buds, and stems. There are many species of it and I probably have at least 2. I also have several systemic diseases that clog their stems, which cause symptoms like dehydration--but no amount of water will save them (in fact, it might finish them off all the faster, by spreading the spores).

Most fungal diseases are active in warm weather, and most of them like high humidity.


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RE: I cant grow rhodys!!

atash, soil-borne pathogens are pretty much omnipresent - they exist in virtually all soils. Most tend to be opportunistic, remaining dormant or inactive for long periods of time until the right set of conditions encourage reactivation and their spread. So they aren't exactly new or more prevalent, only that they are becoming more readily recognized and better known and understood.

Phytophthora cinnamomi, the strain that most affects rhodies in our area, is such a pathogen. It is almost always encouraged by improper cultural conditions like overwatering and/or poor drainage, although other stressors can contribute to its spread as well. It is a root rot and is NOT spread by overhead watering (although other fungal problems can be). It attacks the plant's vascular system and results in the wilt-like symptoms and typically, death. It is far easier to prevent than to successfully treat. Trichoderma harazianum, the active ingredient in 'Root Shield' is effective in combatting P. cinnamomi but it needs to be applied as a prophylactic measure at planting, rather than a remedy after the disease is identified.

P. ramorum, aka Sudden Oak Death, also affects rhodies but is an air-borne pathogen. It is far less likely to cause death in rhodies (but is a serious problem with other species) than P. cinnamomi and is more often referred to as Phytophthora blight, as it causes tip blights and stem dieback. Currently, there is no effective control for this pathogen.

Generally, when soil-borne pathogens are known to be active in your location, one should avoid susceptible plants or at the very least, locate them in areas away from where the pathogen is known to be. And follow proper planting and cultural practices religiously - prevention is the best cure :-)

hobbittmom, I have no idea where in the PNW you are located, but if you are anywhere in the greater Seattle area, drop me an email and perhaps I can offer some more specific advice.


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