I planted two Zepherine Drouhin roses north of a very dense alligator juniper. When they reached six feet in height in their fifth year they were tall enough to get a full six to ten hours of sun in summer. That's when they started to bloom.
It's been worth the wait.
Note that the hammock is almost always in full shade but the rose from about waist height on up is in full sun through most of the day in late May, June, and early July.
