May is a suitable time to commence rose pruning in many districts with the exception of areas subject to heavy frosts where pruning may stimulate new growth that is vulnerable to damage. Most roses are grafted and it is always important to look for and remove any suckers that arise from near ground level and appear different to the top growth. These are from the rootstock and will eventually swamp the plant if not removed.
Prune away any dead or very old branches from the base and middle of the plant as this will stimulate the production of healthy new branches. Old branches are generally grey with aged looking bark, newer branches tend to be smoother looking and greenish or reddish coloured. Also remove any branches that cross over to open out the centre of the plant as the better air flow this creates will help prevent fungal leaf diseases such as black spot and powdery mildew.
Once pruned, give the plant a boost with some fertiliser to stimulate the new growth. Aged manure and blood and bone are great, adding not only plant food but also organic matter which helps to retain the nutrients. Commercial fertiliser especially formulated for roses is also good, and there are some great Australian companies producing excellent fertiliser products. Once you have applied your chosen fertiliser, water in and top the soil with a good layer of mulch to add more organic matter. Hay, compost, leaf mould and wood chips are all good choices for mulch. A very thick layer of wood chips can lock up nitrogen, add some extra nitrogen once in a while if this is a problem.