Choose pest- and disease-resistant varieties
Choosing the right variety is the single most important thing for avoiding common rose disease problems like black spot. There are several roses native to the Willamette Valley that offer delicate pink blossoms in spring, and beautiful hips in fall that attract wonderful wildlife to your yard.
- Native Nootka and Bald hip roses are good choices for a hedgerow, thicket or large space, as they spread by root runners.
- Portland Rose Festival's official rose for 2013, "Pop the Cork" is a disease-resistant hybrid tea rose, as is the fragrant "Sugar Moon."
- "Altissimo" is a tough and gorgeous climber.
- Other great performers include "Knock Out," "Drift," and "Flower Carpet."
For more ideas, search online for disease-resistant roses or visit local rose gardens for inspiration.
Give good sun and ventilation
- Roses need at least six hours of direct sun during the summer to be healthy.
- They also need good airflow to reduce common fungal disease. Plant them with plenty of space so they are not crowded by other plants and use mulch underneath, not groundcover plants. Prune heavily in February or March. Then, as the season progresses, prune out stems growing toward the center to keep good airflow. You should be able to see through the plant in at least a few places.
Ensure rich, organic soil
- Avoid compacting the soil with frequent stepping around plants.
- For a dependable fertilizer, the Portland Rose Society sells an organic blend you can apply a few times throughout the season.
- With any fertilizer, do not apply more than the label says – too much can lead to pest problems, especially aphids.
Use least-toxic pest control methods
- If aphids or other pest insects do come in large numbers, squish them with your fingers or blast them off with water from the hose.
- Use insecticidal soap for a problem that isn't going away, but remember that a few pests are good as they keep the pest-eating insects and birds around your garden to help prevent future problems. Make sure to spray under the leaves where the aphids congregate. Requires repeat application during aphid outbreaks.
- Diseases are trickier to control. If you've provided good soil, sun and air and still have a big problem, try horticultural oils such as Neem oil, Jojoba oil or sulfur sprays, all low-toxicity fungicides. Always follow label instructions since even organic products come with hazards and the label is the law.
- For solutions to specific pest and disease problems, contact OSU Extension Service.