Who discovered the poinsettia?

The poinsettia was not "discovered" in the traditional sense, as it's a naturally occurring plant. However, the person credited with introducing it to the United States and popularizing it as a holiday plant is Joel Roberts Poinsett, the first United States ambassador to Mexico.

Here's the story:

* Poinsett was in Mexico in 1828 and saw the bright red bracts (modified leaves) of the plant, which were commonly used in local celebrations.

* He was impressed by their beauty and sent some cuttings back to his home in South Carolina.

* He propagated them in his greenhouse and shared them with others.

* The plant became associated with Christmas in the US due to its festive red color and the fact that it blooms during the Christmas season.

Therefore, while Poinsett didn't "discover" the plant, he played a crucial role in bringing it to the attention of the United States and making it a popular symbol of Christmas.