I have a garden on top of Chehalem Mountain above the Willamette Valley, East facing. Lots grows here and in fact lots grows in the spot I am discussing. Pretty much everything is well drained despite clay soil, and I had a very large glazed clay pot with a rhododenron doing well surrounded by peonies, the fairy roses, oregano and rhubarb. I took the rhodie out of the pot and planted it in the soil so it could grow as large as it liked and I could "harvest" the pot for another use. The rhodie not only did not thrive, but wilted and browned. I watered it by hand and sometimes it looked like it might revive, but then died and turned crispy. I pulled it out, roots etc unremarkable, and planted a box ball in it's place. The same thing happened to the box ball, it looked as if I never watered it (though you can believe I did!). Both box and Rhododendron grow great for me all over. What could be the story?