They'd almost have to be added alongside it because so many entries already say "evergreen" and fall into only one of the two categories. How would you know which one should replace the general "evergreen" category?
I suppose the process could start with a script to add "broad-leaf evergreen" to all of the plants in the Rhododendron, Pieris, and Ilex genera. Maybe Evan can think of some others.
I'm not sure whether the term should be "broad-leaf evergreen" or "broad-leaved evergreen." I think both are acceptable. Does anyone have a preference?