I staked my huge rose bush yesterday with a copper pipe. Someone told me this morning that the copper pipe will kill my rose bush. Is that correct? Should I remove my copper pipe and use something else? Any suggestions? Is PVC ok?
Some rosebushes do have an allergic reaction to copper in fungicidal sprays containing copper, but not copper used for a supporting trellis.
The reaction to those sprays can be small red spots on the leaves of the rosebush often followed by yellowing of the leaf, then defoliation. The ammoniacal copper used in some of the fungicidal sprays was thought to be safer. It was advised not to apply the copper fungicides on a cloudy day when the solution would tend to stay on the leaf surface in its wet form longer, thus leading to a higher chance of a negative reaction to the spray.
All of the above being said, metals of various kinds have been used for trellises to support climbing roses and other climbing plants for years. I have seen some beautiful copper trellises with their greenish patina that really look great with the rosebushes foliage and blooms, some in the rose beds of my Rosarian friends. I have not heard or ever read of a rosebush having a reaction to the copper in such trellises. I suppose if there were to be a negative reaction it might be from the copper in the ground at the root zone. To help protect against such a negative reaction the portions of copper that go into the ground could be coated with four coats of a good quality spray on paint, or even covered with some PVC piping sealed at the bottom in such a way as to encapsulate the copper away from soils contact but only if you desire to do so. There is no information readily available that shows copper contact will kill a rosebush. There is some mythical information on the internet about using copper spikes and such to kill shrubs, yet more information from Arborists and such that it is a myth.
Although metal trellises are beautiful and ornate, they should be avoided with more tender plants such as; sweet peas, beans and morning glory this is due to the fact that they heat up with the sun and can actually stunt plant growth or burn the tender foliage, no any chemical reaction.