If you’ve had roses growing for 10 years or more in the same spot, dug them out and replaced with new roses, the chances are the new ones will not flourish. This is due to rose replant disease. The cause of this is not well understood but is thought to involve nematodes. If you are replanting roses it is a good idea to change the soil. For each new rose, dig a hole approximately 45cm square and replace it with soil that hasn’t grown roses before. The old soil can be used for growing anything apart from roses.
With large beds of roses it can be quite a job and an alternative to replacing the soil is to grow a green manure crop such as tagetes and dig it in whilst in flower. This is supposed to remove rose sickness but there is only anecdotal evidence as to its efficacy. Another useful product against rose sickness is Rootgrow, a beneficial fungus which adheres to the rose root and rapidly expands to allow the plant access to moisture and nutrients from a wider area of soil thereby increasing the early vigour of the rose.
If you don’t want to dig out your soil, we recommend Rootgrow, which is a ‘friendly fungi’ that can be sprinkled in the planting hole. This helps the roses overcome any re-plant problems.