Posted: 25/01/2013 at 18:31
There are a few things to consider here. Are the branches that flowered growing from below the graft (a thickening of the main stem sometimes just above or below soil level). If it comes from below the graft and it is an oldish plant then it could have reverted to the root stock, probably rosa canina or dog rose (?). These days they are grafted onto apple root stock so there is no danger of these 'suckers' which are very vigorous and take energy away from the rest of the plant. The other thing to consider is as mentioned above, the danger of rose repeat disease and according to a T.V. programme about a year or so ago, you can avoid having to replace/sterilise earth by planting the new rose in a cardboard box. By the time the roots grow through it the plant is strong enough to withstand whatever causes this disease.