Where did the poinsettia tradition begin?

As a shrub growing wild in southwestern Mexico is the way in which poinsettias (Euphorbia pulcherrima) started out.

Left to its own devises, the poinsettia matures to a height of 16 feet/4.9 meters. But the beautiful color change that its modified leaves take on by late December got the attention of the indigenous peoples of Mexico. At that point, it transitioned into a cultivated plant whose height was controlled to about one-third of its potential.

As a cultivated plant, it became incorporated into the religious rituals of the ancient Aztecs of Mexico and subsequently into the Christmas celebrations of Spanish-speaking Catholic missionaries and settlers of Mexico. The association with the Christmas holidays was continued with the plant's introduction into the United States of America by Joel Roberts Poinsett (March 2, 1779 - December 12, 1851) and its cultivation and promotion through the efforts of the Ecke family in early 20th-century Hollywood, California.