The plant-on trim elements are trim elements attached to door and window openings or elsewhere on a building made of stucco or similar material. The plant-ons have a foraminous lath shell and a mating core, with the core having one or more (preferably a series of) reliefs formed therein, e.g. along the outer corners of the core. The reliefs allow stucco or other suitable material to flow completely through the foraminous lath and encapsulate the lath at the relief areas, thereby providing a much stronger bond between the coating material and the underlying lath shell. The foraminous material may be expanded metal or metal or plastic screen, while the core may be formed of foam plastic, wood, or other suitable material.