1. Flowers are different: milkvetch flowers are orange-yellow or purple-red in color, and the flower stems are hollow and cylindrical. Alfalfa flowers are purple in color, with butterfly-shaped corollas. The flower stems grow from the roots and have many branches.

2. Different growth habits: Milkvetch likes warm and humid environment and is not cold-tolerant. Alfalfa has corresponding cold and drought tolerance.

3. Different lifespans: Alfalfa has a longer lifespan and can survive for six or seven years.