Morphological characteristics and growth environment of the following common grasses:

1. Sorghum: Sorghum is a common sorghum plant in summer. Its height is generally above 1 m, its stem is stout and its drought resistance is strong.

2. Setaria viridis: Setaria viridis is a perennial herb, about 50 cm high, with slender stems and curved leaves, which grows on grasslands and roadsides.

3. Alfalfa: Alfalfa is a perennial herb with a height of about 60 cm. Its stem is stout, its leaves are composed of three leaflets, and its corolla is purple. It grows on grasslands and cultivated land.