The “Under the Mistletoe” project was developed to capitalize on student curiosity about the American Christmas Mistletoe plant and draw learners into an engaging, inquiry-based exercise that incorporates numerous life science standards and collaborative research. By collecting data on host and nonhost tree size, location, and number of mistletoe present during the winter months—after the trees have lost their leaves—students investigate the host-parasite relationships of mistletoe. Students gain experience developing research questions, using scientific equipment to collect data, and drawing conclusions based on the integration of math and science.