An advertisement of Zephirine Drouhin rose said that this rose was disease resistant, shade tolerant, alkaline soil tolerant, pollution tolerant, more floriferous than other varieties, and completely thornless. I suppose they are probably being optimistic about it: I would especially like to know about the thornlessness. Are these really completely thornless?
I have a Zephirine Drouhin Rose that has been growing in USDA zone 4 for two years. It puts on a great show, grows fast, resistant to powdery mildew but it is not thornless.
Compared to the shrub roses I have you can work with it without gloves. There are not many thorns, perhaps one every inch on the larger stems only. The thorns are a 1/4" in length and as picky as you would expect.
The Bourbon rose is also known as 'The Thornless Rose'.
This is one of the classic roses, introduced in 1868 and cherished for generations for its lavish and unsophisticated flower display, and its ease of cultivation, not least the thornless stems which make pruning a pleasure.
Source: BBC Gardening
davesgarden.com mentions 'Stems are nearly thornless'
I grow this beautiful rose, so from personal experience I can tell you that mine is completely thorn less! (I wish all the roses were like this) It grows on one end of a pergola in my rose garden. You can learn more about this rose here: http://www.allaboutrosegardening.com/Zephirine-Drouhin-Rose.html