First, the rhizome difference:

The rhizome of Acorus calamus is thinner than that of Acorus calamus, the former is light brown outside and the latter is yellowish brown.

Second, the difference between the blade:

Acorus calamus leaves are sword-shaped, with sharp apex and luster, and the midvein is not obvious. Acorus calamus leaves are basal and sword-shaped.

Third, the difference of flowering period:

The flowers of Acorus gramineus are small, dense and yellow-green. It blooms from April to May, and the flowers of Acorus calamus are yellow-green. The flowering period is from February to September.

Picture comparison:

Stevia rebaudiana

calamus