Left unpruned or lightly pruned this rose can get pretty enormous: mine is currently about 10' x 12'. It was planted back around 2004 or 2007; it's in too much shade and may be trying to get out to the sun; I didn't get around to pruning it last winter. It's a massive shrub, healthy, but has never bloomed well, tending to set a lot of buds but then not opening them in great numbers. The lack of sun may be a problem.

would someone please tell me how big these blooms are supposed to be? i was given a rose that has been in a friend's famly gardens for 4 generations. Alas, no photo. Cluster flowered, the plant is supposed to be smothered in blooms and strongly scented, true white.

The Magazine of horticulture, botany, and all useful discoveries, Volume 23 page 263 (June 1857)
The Rose.--No. 5
Prof. C. G. Page, Washington, D. C.
It cannot be thought chimerical to look forward for roses combining the qualities of constant-blooming, strong-growing, fine forms, colors and odors, entire hardiness and even thornless branches, where art shall reverse the lover's lament by stealing the thorn and leaving the rose. This latter quality has been fully attained in the hybrid perpetuals, Delphine Gay and Blanche Vibert, and nearly so in William Griffith, one of the most perfect roses grown. I have seen vigorous shoots of it, six feet high, without a thorn.

Available from - Rosen von Schultheis
http://www.rosenhof-schultheis.de/Suche/artikel_3047_Blanc_de_Vibert.html