The following was received via email: In a book on rhodos which I recently purchased in the U.K. there is the following mention of R. ponticum: "As well as being used as an ornamental in its own right, R. ponticum was widely planted as game cover throughout Britain and Ireland, and was extensively used as a rootstock for grafting less vigorous but floristically superior forms. Its vigour and tendency to spread rampantly, however, with its ability to render the soil beneath it poisonous to other plant species, is a legacy that can still be seen." The part that surprised me was the fact that it renders the soil poisonous. Is this true? Secondly, this spring I noticed a couple of plants purchased from reputable nurseries via the VanDusen plant sale (Christmas Cheer & Taurus) had obviously been grafted onto R. ponticum, as they both had strong growth of that species which, after consulting with a rhododendron society member, I cut off to the base. So my second question is how many of our local plants are grafted onto R. ponticum - do you have any idea? With our mild climate I am puzzled as to why this is necessary unless plants are sold further afield in British Columbia where the winter temperatures dip lower than here. I guess these 2 queries are linked as I wonder if the roots of R. ponticum contaminate the soil as the book I have states they do, in which case should I dig up my Christmas Cheer & Taurus? Also, is there any way of checking in future which plants are grafted, because it certainly isn't apparent to my inexperienced eye.