Unfortunately, there are a number of insect pests who enjoy roses as much as we gardeners do. In order to have beautiful blooms to enjoy this spring and summer, it is necessary to provide winter care to our rose bushes to thwart those pests.
Some insect pests overwinter in the soil at the base of the rose bush, while others leave their eggs in the debris of old leaves; still others burrow into the cane to leave their eggs. Rose leaf diseases, such as powdery mildew and black spot have an advantage in dense foliage, poor air circulation and leaves left on the plant from the previous season.
Dormant rose pruning combined with horticultural oil spray can ruin the party for these pests and diseases. While the temperature in the Central Valley winter isn’t cold for long enough to cause the rose bush to become completely dormant, our bushes do demonstrate slowing of growth and reduced blooms. It is healthy for the plant to have a period of time to only produce a good root system during our “rainy” season. We can foster this by first allowing the rose blooms to die on the bush starting in November. This allows the plant to produce rose hips and slow new flower production.