Alfalfa is one of many introduced legumes. The most distinctive characteristic is its tightly coiled seedpod, whereas most other legumes have seedpods that are more or less straight. The leaflets of Alfalfa are shaped somewhat differently from other legumes, as their coarsely toothed outer tips look like they have been chopped off, while their sides are smooth and wedge-shaped. There is a similar introduced species in the same genus, Medicago falcata (Yellow Lucerne), that has yellow flowers and seedpods that are less tightly coiled. However, it has been observed in only two counties in Illinois. Sometimes Alfalfa is called Purple Lucerne.