My experience with the three varieties: Roseum Elegance is an old "iron clad" hybrid that will eventually reach 6 feet or more, but not very rapidly unless growing conditions are ideal. Holden is something of a mystery. In my experience, the plant itself is quite hardy, but the flower buds are not. If temperatures fall much below 0, no flowers. It is also a slow grower and I doubt very much that 6 feet is a realistic height unless we are talking about decades of growth. Landmark is to my eye a harsh color. It is also semi-deciduous in most winters. It is extremely hardy, however, and can be grown in full sun. Protection from winter sun and wind especially in newly planted rhododendrons is important. Burlap barriers are a good form of protection but should not touch the plants as it would if wrapped around them. Use stakes, etc. to support the burlap.

In certain areas of the country such as the PNW certain varieties of rhododendrons can probably make effective privacy screens. For areas like MI and other states which experience cold winters, they are far from ideal for your intended purpose. They just do not grow dense enough or rapidly enough to provide much in the way of privacy until many years have passed.

Thanks for your response. I've decided to return Holden based on your feedback and my concerns about its height. It's very hard to find real-life information on that rhododendron. If anyone else has any please share! I'm leaning toward keeping the Roseum Elegans and possibly putting it at a point along the fence that does not need as much height quickly, but which can handle some eventually. Still deciding about Landmark. I'm OK with semi-deciduous, but not sure about the color or height. Your information on winter protection is good to take into consideration. I've read different accounts on best practices for this area.

CuriousHomeOwner: I know exactly what you mean about reliable information about Holden. I have seen it listed as hardy to -15 and hardy to only 0 in rhododendron books by experienced growers and authors. After this past mild winter, buds looked great. Low 20's toward the end of April and not a single flower. It may be that absolute winter cold is not the problem as much as low spring temperatures after the buds have begun to swell.