Stems and branches
The branches on many of my roses are dying back. What causes this?
Branch dieback on roses is very common, and it is unusual to see a rose bed without at least a small amount of die-back. There are a number of different causes.
Die-back can be a symptom of the root problems described above, as the plant struggles to take up water through its poorly-functioning root system.
Sometimes the die-back is the result of a fungal pathogen colonising the branches themselves. The fungi found most commonly are Paraconiothyrium fuckelii (a cause of rose canker) and Botrytis cinerea (grey mould). These fungi are quick to colonise the branches of roses that lack vigour (due to pests, foliar diseases, nutrient deficiencies, etc.), or branches that have suffered physical damage (e.g. from frost or poor pruning technique). Many of these factors can cause dieback in their own right, but colonisation of affected branches by the die-back pathogens can greatly increase the severity of the problem.
The stems and branches of my rose are covered in small, brown, limpet-like structures. What are they?
These are scale insects. The species found most commonly on roses is brown scale. A flat, circular whitish scale known as scurfy rose scale can also encrust the stems
Why has my plant developed a large, knobbly swelling near the base of the stem?
The most likely cause of this symptom is a bacterial disease called crown gall. The roots can also be affected.
How can I identify suckers on my grafted rose, and what can I do to prevent them from occurring?
Suckers (shoots produced from the rootstock) will develop from below ground level, and their leaves will often differ in appearance from those of the rest of the plant. For example, they may be a different colour (often paler) and/or have a different number of leaflets.
Suckers often develop if roots are injured, so avoid damaging the roots during digging or hoeing. To remove a sucker, dig down to expose its origin on the root, and then pull it away at this point; don’t just cut it off at soil level, or it will regrow.
If a rose is growing on its own root system it may still produce suckers from the roots, but these shoots will be identical to the rest of the plant and can even be used for propagation.