Research was conducted to equip Iowa producers with more accurate corn planting date information based on their specific location. Objectives for this research project addressed during the presentation include: 1. What are the optimum planting windows for maximum yield? 2. How do new recommendations (2006-2009 data) compare to previous ISU recommendations (1998-2000 data)? 3. What are the risks associated with planting outside the optimum window? 4. How is plant growth and development impacted by varying planting dates? 5. Are grain yield differences correlated with differences in growth and development?