Ask Mr. Smarty Plants

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.