Sounds like my cup of tea. However, I have no information.

In my opinion it is well worth a visit. The collection consisted of 2500+ species/cultivars of plants, most of which are probably still alive and well. Besides Rhododendrons including hundreds of unusual vireya, maddenii, yakusaminum and big leaf species and hybrids, there are also mature and huge examples of other rare shrubs and trees from other parts of the world. There used to be a lot of unusual perennials as well but these appeared to be going into decline the last time I visited, mostly because of overcrowding from larger shrubs and trees. I visited the Gerdemanns (fabulous hosts) in 1999, 2002, and 2006. In the last couple of years the property exchanged hands, Jim passed away and Janice moved to a smaller house in Yachats. I have been in contact with the new owners who seem intent on maintaining the collection more or less as is, but with gradual improvements to public access. It is a difficult site to make very accessible since it is steep, wet, and forested, and surrounded by residences with little available parking.

Here are some pictures I took on my visits in 1999 and 2002.

1999 pictures

2002 pictures

Thank you Ian for sharing the pictures and your thoughts. It looks like a fabulous place and I will look forward to planning a visit.