Veilchenblau, an old-fashioned rambling rose is also sometimes called Bleu Violet, Blue Rambler, Blue Rosalie and Violet Blue. Its relatively small semi-double flowers are purple to blue-purple to gray-mauve , depending on climate, sun exposure and individual flowers' maturity.
The plant is large and can grow 15 to 20 feet tall and 12 feet wide. Canes are virtually thornless, with glossy, light to medium green leaves. The semi-double flowers are borne in large clusters in the spring, with no repeat bloom. The buds are purple, opening to purple streaked with white. As the flowers age, the color fades to gray-mauve. Veilchenblau's fragrance has been compared to that of lily-of-the-valley or green apples.
Introduced in Germany in 1909 by breeder J.C. Schmidt, Veilchenblau has sometimes been called "the blue rose." It is descended from Rosa multiflora, a prolific, cluster-flowered species native to Japan and Korea.
Veilchenblau is quite cold tolerant, surviving in USDA zone 4b (winter temperatures as low as minus-20 degrees Fahrenheit) and warmer climates. The plant can also tolerate some very light shade. Ideal conditions for this rose are identical to those for most other roses: rich, loamy soil, abundant sunshine and regular moisture (though not wet feet). The plants benefit from generous mulching as well.
Because of its fragrance and thornless nature, Veilchenblau is very suitable for use near heavily trafficked areas. It can be trained on arbors and trellises, but like all climbing and rambling roses, needs to be tied to a support. Rosarian Graham Stuart Thomas recommended growing the shrub against a shaded wall. Because of its once-blooming nature, it might be combined on the same structure with another repeat-blooming rose of a complimentary color. An example of this is the climbing form of Iceberg.
Veilchenblau cannot generally be obtained from local nurseries and garden centers, but is available from vendors selling heirloom or old garden roses.