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What is wrong with my rhodie?

Posted by gogaylego MD (My Page) on
Tue, Oct 3, 06 at 18:36

I planted this Rhodie in the Spring of 2005. It made it through the hot summer, fall, and winter. Looked pretty good this Spring. We had a very hot summer here in MD, with below average rainfall.

My Rhodie now looks quite bizarre! There is a section that looks fairly healthy, with new growth. There is a section with wilted, yellowing leaves. There is another section completely devoid of leaves.

Does anyone know what is happening, and if it is reversible?

Thanks,
Gayle


Follow-Up Postings:

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RE: What is wrong with my rhodie?

I should have mentioned that this is a Roseum Elegans. It is planted in the same area of my yard where 5 azalea are thriving.


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RE: What is wrong with my rhodie?

Drought or Borers can cause Entire portions of a plant die:

* Drought can cause entire branches or entire plants to die. We have had several years of drought here and we observe that if rhododendrons and azaleas are not watered during a drought some plants will die, but others will just have one section of the plant die. It seems to be the plants way to conserve what little moisture it has. Prolonged drought weakens plants and often results in the appearance of fungal cankers on the branches of older azaleas. Look for branches that wilt in hot, dry weather in late summer and be sure to water azaleas if drought drags on more than a few weeks. Prune out the affected branches to stop the spread of fungal canker diseases.

* If a Rhododendron Stem Borer, Oberea myops, or Rhododendron Borer, Synanthedon rhododendri, is in a branch, the entire portions of a plant beyond (away from the roots) will wilt and die. Borers only affect the portion of the plant away from the roots from the borer. If the borer is in the main trunk, then the entire plant will wilt and die. The plant can be saved by cutting off the area with the borer and letting the plant regenerate from the roots. There are no conventional insecticides that will kill stem borer larvae once they are inside the branches. The best control option for homeowners with only a few plants is to prune out and destroy wilting branches in early spring or late summer.

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


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RE: What is wrong with my rhodie?

Thank you rhodyman! I set up a watering system this summer since it was so dry, but I traveled for work quite a bit and don't know how diligent my husband was with the watering (and for Pete's sake, all he had to do was turn on the spigot!). I will go out and inspect the plants later today for fungus, but I don't recall seeing anything like that. However, the wilting has only just started in the last few weeks, past the worst of the drought. So perhaps it is a fungus. I don't know how to tell if I have Borers, but will read the suggested link and see what I can find out.

Thanks!
Gayle


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RE: What is wrong with my rhodie?

  • Posted by morz8 Z8 Wa coast (My Page) on
    Wed, Oct 4, 06 at 21:21

Borer damage isn't hard to detect...

I was curious too if you remember when you planted this if you loosened the rootball well to allow roots to venture out into surrounding soil. Rhododendrons can be very hard to keep adequately watered if the roots remain in the container shape (assuming it was purchased in a container).
If the roots remain in that compact shape, the plant may do well for a year or so and begin to fail at two or three.

Here is a link that might be useful: Rhododendron borer


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RE: What is wrong with my rhodie?

Hello, I have 3 of these plants and they are 2years old and have never bloomed. And they have black spots on the leaves and are not very full what can i do? Penny


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RE: What is wrong with my rhodie?

"These plants" could be about anything from Deciduous Azaleas to Evergreen Rhododendrons. Since we are speaking in generalities, here are some general problem areas:

NO FLOWERS:

There are a number of reasons for a lack of flowers. The effect of each variable depends upon the variety of the plant. The effects include:

* Pruning. The buds are formed in late summer and early fall so pruning then or later is not advisable since it will remove flower buds. New leaf buds will form in the spring, but new flower buds won't form until the next year.

* Variety. Some plants will never bloom. Some rhododendrons that come from the seed of a hybrid plant will look good but will never produce flowers or will produce very poor flowers. To come true to the parent plant, a hybrid may be propagated by cuttings or tissue culture but not from seed. A good hybrid seedling only comes about once in a while. For that reason it is important to know that you are getting a good named variety or a good species.

* Fertilizing. Nitrogen promotes leaf and branch growth and discourages flower bud production. It can also force late season growth that gets killed or stunted by frost damage. Phosphorus promotes flower bud production and hardiness. Potassium is necessary for well being.

* Weather. Cold weather can kill flower buds. Usually you see the brown buds in the spring. Cold spells in the fall or spring can damage buds that are not hardened off. Bud blast (blooming in fall or winter) uses up good buds which are then not available at the normal blooming time.

* Age. Most rhododendrons take 2 to 3 years to bloom from a rooted cutting unless forced. Some take longer and some bloom sooner. From seeds the plant may take 1 or 2 additional years.

* Sun & Shade. Some rhododendrons need full sun to bloom and others can take fairly dense shade. In general, the more sun the more flower buds but also the greater exposure to damage from desiccation in summer or winter. More shade produces tall spindly foliage and less flowers.

* Inspection. You can usually tell if the plant has ever bloomed. A rhododendron that has bloomed will have the seed pods on it unless it has been dead-headed. If dead-headed too late after blooming, new flower buds can be damaged.

BLACK SPOTS ON LEAVES:

* Pestalotia leaf spot. If a leaf has brown areas with white spots, it probably has a local fungal infection of Pestalotia leaf spot. This is seldom controlled with fungicides and is best mitigated by good sanitation and avoiding excessive moisture.

* Lace bugs. Whitish specks on the upper surface of leaves and dark spots varnish-like on the bottom are symptoms of rhododendron lace bugs, Stephanitis rhododendri, and azalea lace bugs, Stephanitis pyrioides, small insects with transparent wings on under-surface of leaves.. This insect hatches early in spring as the new foliage begins to mature and its numbers may build to damaging levels with successive generations. Lace bugs reach their peak in late summer and do their worst in sunny, exposed sites. Spiders are important predators of lace bugs and since they shy away from sunny, hot places, plant your azaleas where there is some shade. Insecticidal soap, horticultural oil, or a systemic insecticide may spare your azaleas the damage if applied in spring when the first hatchlings are noticed. Care must be taken to spray the lower surfaces of the leaves where the lace bugs live. Moving a plant to an area with more shade may alleviate the problem. Lace bugs are more prevalent on certain varieties. The following azalea cultivars have resistance to azalea lace bug: ‘Dawn,’ ‘Pink Star,’ ‘Ereka,’ ‘Cavalier,’ ‘Pink Fancy,’ ‘Dram,’ ‘Seigei,’ ‘Macrantha,’ ‘Salmon Pink,’ ‘Elsie Lee,’ ‘Red Wing,’ Sunglow’ and ‘Marilee.’

* Physiological spots. Brown, reddish-brown or purplish leaf spots that occur on many cultivars, including R. 'Blue Ensign' and R. 'Mrs. G. W. Leak', are physiological and not disease caused. These spots are generally purplish and are inherent in the cultivar. Environmental stress may increase their appearance. They do no harm to the plant.

* Necrotic ring spot. Some leaf spots are caused by a virus thought to be a potexvirus, the most common ailment being called necrotic ring spot. The symptoms are reddish-brown rings or spots on the leaves. It generally occurs only on the two year leaves of a few rhododendron cultivars such as R. 'Unique', or on Kalmia latifolia. It also appears on the first year foliage of some R. 'Loderi' clones. Little is known about the disease and a does not seem to spread from one cultivar to another. No control is known or generally necessary.

* Chemical injury. Leaf spotting can also be caused by chemical injury, such as drift from cleaners, paints, or chemicals used to kill moss on roofs. Sometimes the results of such injury may not show up for weeks or months.

* A fungus. There are a number of leaf spots or burns caused by fungi such as Botryis, Pestalotia, Phyllosticta, Septoria and others. Many are secondary infections happening after mechanical damage or environmental stress, such as sunburn, drought, winter damage or windburn. They generally occur during wet weather and many times are self limiting with drier weather. Good sanitation is helpful, so remove brown and fallen leaves. Also provide good air circulation. Spraying with Benomyl or similar fungicide can be useful, but is frequently not necessary.

* Phomopsis. Phomopsis rhododendri symptoms vary from leaf spots to chlorosis 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.

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


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RE: What is wrong with my rhodie?

My rhododendrons look just like these. They are on a south facing bring wall & I didn't water them very much this summer during our long hot spell. I was thinking about transplanting them to another place in my yard. Can I transplant them now or should I wait for early spring?


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RE: What is wrong with my rhodie?

Now is the best time. Keep them watered after transplanting, even during the winter, but make sure they have good drainage. Then they will have time to establish their roots in the new location before the stress of a hot summer.

Mulch them well to prevent frost heaving in the winter and to conserve moisture in the summer. Do not spread the mulch up against the trunk of the plant, this will invite vole damage.


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