When roses are registered, they have gone through several years of testing. If in the microclimate the rose was tested in, the average mature growth is four feet, that is the information which is included in the registration.

However, roses are variable. The perform differently in different microclimates. You did not mention whether or not you had your rose planted in full sun, partial shade or....

Roses, planted in areas where they do not get enough sunlight will often "reach for the sun", which can explain the height difference. But if that is not the case, this rose must favor your microclimate over the one where it was tested and is putting out much taller growth than expected.

A lot of the David Austin roses, reputed to grow to only three feet, will become huge climbers in the southern California microclimate. That is because they get less chill hours and a lot more sunlight.

Sometimes, roses will surprise the breeders by growing a lot larger and a lot taller in different microclimates.

Smiles,

Lyn
helpmefind.com