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Mr. Smarty Plants - Problems with rhododendrons in Germany

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Monday - July 07, 2008

From: Frankfurt, Germany
Region: Other
Topic: Shrubs
Title: Problems with rhododendrons in Germany
Answered by: Barbara Medford

QUESTION:

I am writing with questions about rhododendrons. I purchased four small rhododendron/azalea hybrids in April. Because I had to prepare the garden before planting them, I left them in the pots they came in for almost 4 weeks. During this time they flourished, flowered and looked quite healthy. I noticed new growth and was not concerned about their health at all. I planted them in my garden in early May, and about three weeks later the leaves began to curl, turn brown and fall off. Two of the rhododendrons were quite badly affected and lost almost all the leaves. The other two were only mildly affected. I took a sample of the leaves back to the nursery where I bought the plants. The employees thought a fungus was attacking the plants and gave me an anti-fungal powder to mix up in my watering can. I applied this once, and about a month later began to notice new growth on all four rhododendrons again. The two rhododendrons that lost most of their leaves have only come back on half the plant. The other half looks like little brown sticks. Should I cut those back, or let them be? Yesterday, I noticed one of the rhododendron's leaves curling a bit. I used the anti-fungal stuff again in case the same problem is returning. Do you agree this sounds like a fungus? If so, is there anything else I should be doing? I appreciate any advice you can give, as I live overseas and have trouble communicating with the people here who might know what's wrong. Thanks for your time.

ANSWER:

We do sympathize with your problems trying to grow plants in a country where you are not totally familiar with conditions. Unfortunately, that is also our problem in trying to help you. The Lady Bird Johnson Wildflower Center is dedicated to the preservation, planting and propagation of plants native to North America. By the same token, we would expect that plants native to Germany, and to the area of Germany in which you live, would be a better choice for you. Because we operate in North America, we would have no information on whether rhododendrons were native to Germany, nor do we have any way of knowing what climate and soils you are dealing with.

Probably the best we can offer you are some websites with very general information about rhododendrons and azaleas, and you can try to apply the information to your particular situation. For instance, rhododendrons are considered woodland understory plants; they need acid soil which they can obtain in the woodlands from fallen leaves and pine needles. Planted in an alkaline soil, they are threatened with chlorosis, loss of chlorophyl in the leaves, because the roots are unable to access the needed trace elements of iron and manganese in alkaline soil. First, try this Ohio State University Extension site on Maintaining Healthy Rhododendrons and Azaleas in the Landscape. This Azalea and Rhododendron Diseases site from Clemson University Extension might help you diagnose the problems you are having. Finally, from The Master Gardeners, this article on Caring for Rhododendrons

 

 

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