Flower Color: Red Flower Form: 3-4″ (8-10cm) Single Flowering Period: Summer – Fall Mature Height: 7-10′(2-3m) Pruning Requirement: Light Pruning Planting Aspect: Full Sun Cold Tolerance: USDA Zone 5 Price Group: Standard About Rosa Dortmund Glossy dark green leaves and clusters of open, red flowers with white centers and yellow stamens in summer and autumn. These single flat flowers are unlike many other roses yet very appealing.