Which American was known as a self-taught botanist during the colonial period?

John Bartram is recognized as a self-taught botanist during the colonial period, making significant contributions to the field of botany in America. He established one of the earliest botanical gardens in North America in Pennsylvania and was known for his extensive knowledge of native plants. Bartram's work included the discovery and classification of many species, which were later documented and shared with the scientific community of his time. His passion for botany and his achievements made him a prominent figure in American science, particularly in the study of plants.

The other figures mentioned, while notable in their own right, did not have a specific focus on botany in the way that Bartram did. John Adams was primarily known as a Founding Father and second president, Ralph Waldo Emerson was a central figure in the transcendentalist movement and known for his philosophical writings rather than botany, and Thomas Jefferson, although he had an interest in science, was more famously known for his contributions to architecture and politics rather than specializing in botany like Bartram.