The Rishonim give two reasons for the prohibition of kitniyos. First, because of the similarities to the five chometz grains (wheat, barley, rye, spelt and oat) confusion can occur. Cooked dishes made from kitniyos appear similar to those from the five chometz grains. Furthermore, kitniyos are often ground into a flour that can easily be confused with chometz flour. Finally, kitniyos are often grown in fields adjacent to those in which chometz is grown (and processed on the same equipment or stored together) and the kitniyos and chometz can easily mix together.