The effects of black polyethylene (PE) mulch alone and in combination with plastic film tunnels (Agronet, Reemay, whiteperforated, clear, and clear-slitted) were studied on morphology and yield of sweet corn in North Logan, Utah. Yields of "Miracle" sweet corn (Zea mays L.) were increased significantly by using black PE mulch and with a combination of various types of plastic row covers, as compared to unmulched soil. Standard-growth analysis procedures were conducted to verify responses among treatments. Treatment effects were determined by measuring days to first flowering, ear weight, number of side tillers, cob length, cob circumference, cob fill length, number of rows, and number of kernels missing per cob. Leaf area, plant height, and total shoot dry mass were significantly larger for mulched than for unmulched plants.