Which of the following is not a cultivar of Camellia?

The identifying factor of which option is not a cultivar of Camellia lies in understanding the classifications of these plants. Camellia japonica, Camellia sasanqua, and Camellia reticulata are all species or varieties within the Camellia genus. They are recognized for their ornamental value and horticultural significance, each producing distinct flowers and having specific characteristics.

Calycanthus floridus, on the other hand, is a completely different genus known commonly as the sweetshrub or spicebush, which is not related to Camellia. Therefore, it is not a cultivar or species within the Camellia genus.

In summary, only Camellia japonica, Camellia sasanqua, and Camellia reticulata are part of the Camellia genus, while Calycanthus floridus stands apart as a separate entity, making it the correct answer to the question.