Troubled that she has no pesos to buy a gift for the Christ child, Juanita humbly follows the mystical behest of a stone angel to bring weeds to the midnight mass instead. Miraculously, the weeds transform into poinsettias because they are a "gift from the heart." More languidly paced than Tomie dePaola's tightly spun Legend of the Poinsettia, Oppenheim's telling sags a bit under the focus on the family's poverty and heavy-handed insertions of Spanish vocabulary. Negrin's (The Secret Footprints) striking illustrations, however, energize the tale, taking their cue from the brilliant flowers and sun-kissed colors of Old World Mexico. His mixed-media art creates a lush, dreamlike environment where anything seems possible. A Spanish-language edition (El milagro de la primera flor de Nochebuena, $16.99 -308-7) is available, too. Ages 4-8. (Sept.)