Are holly roots notably aggressive? Some sources (mostly blogspam-ish) make claims like:
The expansion of the out-of-control holly tree roots puts all of your pipes, overall foundation, plumbing, etc. at risk of getting damaged. The best way to prevent this damage from happening is by making sure your holly plants are properly taken care of and considering planting them away from anything the roots could damage should they get out of control.
https://www.conserve-energy-future.com/do-holly-trees-have-deep-roots.php
But some holly varieties apparently don't raise much concern:
These sources don't mention root problems:
https://www.rhs.org.uk/plants/118356/ilex-x-aquipernyi-dragon-lady-meschick-(f)/details
https://plants.ces.ncsu.edu/plants/ilex-x-aquipernyi/
Are holly roots aggressive? Or is this question meaningless without specifying further? My specific cultivar is dragon lady holly. The soil has a lot of clay and gravel below 4-8 inches. There's a gravel driveway on one side with an old plastic "weed barrier" underground that is probably mostly still intact.