One area of my garden has incredibly heavy clay soil. In my experience, amending is necessary, but Porkpal is also very right in saying that you don't want to have the rose sitting in a hole of amended soil, whilst all around it is the heavy, unamended clay. This creates what I've hear described as "the bathtub effect",or as Porkpal puts it, a "sort of well". Water will collect there, but ,even worse perhaps is the fact that the plant has no motivation to send roots out to the surrounding soil-it just sits there in it's little hole. I am trying to amend my entire bed, even removing some of the clay, mixing expanded clay and potting soil into the entire area, but I'm by no means certain that these efforts will prove sufficient! Now, maybe your clay is not as bad as mine, and if so ,you might indeed get away with just digging the rose up and re-planting it with no amendments added to the hole-just a nice, generous mulch of organic matter, better yet with a shovelful of manure on the soil surface. Good luck!
