Focusing on the wildness:
* Cultivated flower: This emphasizes the controlled, planned environment of a garden flower.
* Domesticated flower: This highlights the difference in origin and adaptation, emphasizing the human influence on the flower.
Focusing on the flower type:
* Ornamental plant: This broadens the category to include plants that are primarily grown for their aesthetic value, not just flowering ones.
* Indoor plant: This contrasts the wild, natural habitat of a wildflower with a contained, artificial environment.
Focusing on the environment:
* Garden flower: This directly contrasts the natural environment of a wildflower with a cultivated one.
* Greenhouse flower: This emphasizes the complete control of the growing environment.
Ultimately, the best opposite for "wildflower" depends on the context and the specific aspect you want to highlight.