Common Disease Problems
Edema (Oedema): Leaves become distorted due to excess moisture in the soil. Plants absorb more water than they can use. Burpee Recommends: Do not overwater plants, keep the soil moist but not wet. If drainage is poor add compost or peat moss to improve drainage.
Powdery Mildew: This fungus disease occurs on the top of the leaves in humid weather conditions. The leaves appear to have a whitish or greyish surface and may curl. Burpee Recommends: Avoid powdery mildew by providing good air circulation for the plants by good spacing and pruning. Contact your Cooperative Extension Service for fungicide recommendations.
Rust: A number of fungus diseases that cause rust colored spots on foliage. Burpee Recommends: Remove infected plant parts. Contact your Cooperative Extension Service for recommendations.
Smut: This fungus attacks mostly young seedlings as the new leaves emerge. It causes blister-like lesions near the base of the plant and streaks on leaves. The streaks mature into black powdery spores. The fungus stunts the growth of the plants. More mature plants are not as susceptible. It is most prevalent in temperatures under 75 degrees F. The disease lives in the soil for several years. Burpee Recommends: Some fungicides are effective, Check with your Cooperative Extension Service for recommendations.
Common Pest and Cultural Problems
Cortaderia has few pest issues.
Winter Kill: Cortaderia is sensitive to colder areas and a severe winter may kill the roots. Burpee Recommends: In borderline hardiness zones provide extra winter protection, mulch the ground after it freezes. Remove the mulch in spring.
Can I grow cortaderia in containers? No, it is much too large!
Is cortaderia deer resistant? Yes, it is deer resistant.
Does cortaderia attract pollinators to the garden? Yes, it attracts birds to the garden.
Why didn’t my cortaderia bloom? It may be in too much shade, it needs 6 hours of full sun daily. Another possible reason could be if you fertilize too much this may cause green growth at the expense of flowers. Also, it blooms late in the season and it may be too early.
Do I need to divide my cortaderia? Yes, divide plants in spring breaking the pieces apart with a spade. Be careful as the leaves are sharp. Divide every 3-4 years.