Reducing problems
When buying new stock from reputable growers, ask them to recommend cultivars that are more resistant to certain diseases and physiological problems.
Roses need at least six hours of sunshine each day and should be sited in a bed away from invasive tree roots. Roses are heavy feeders and must be planted into soil improved massively with soil improver or compost. Soils must be free draining and sandy soils should have a clay additive worked into the top 30cm of soil. Feed regularly with a complete fertiliser once established.
Humidity encourages fungal disease, as does poor air circulation. Do not position roses too closely together, avoid overhead watering, and prune to maintain an open structure.
Fortunately, in most parts of Western Australia the climate is generally dry, resulting in good conditions for growing roses.
Herbicide overspray
Roses are particularly susceptible to drift from glyphosate, so care is needed when tackling nearby weeds. The safest method is to paint the herbicide onto the weeds with a brush, rather than use a spray which can easily drift. Glyphosate damage results in bleached, distorted foliage that is almost white. Plants will grow out of it in time.
Physiological problems
Physiological problems are often related to climatic conditions. Bull-heads are short, squat blooms triggered by low temperatures. Sometimes, leafy calyces develop, or leaves are seen emerging from the centre of a bloom
This is also climate related. Some rose varieties are more prone to physiological problems.