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'.
Source: BBC Gardening
davesgarden.com mentions 'Stems are nearly thornless'