genus calamagrostis

NOUN
19 LETTERS · STARTS WITH G

genus calamagrostis is a valid 19-letter word worth 24 points in Scrabble and 31 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS
G2E1N1U1S1C3A1L1A1M3A1G2R1O1S1T1I1S1
2 + 1 + 1 + 1 + 1 + 0 + 3 + 1 + 1 + 1 + 3 + 1 + 2 + 1 + 1 + 1 + 1 + 1 + 1 =24 PTS
DOUBLE WORD → 48TRIPLE WORD → 72
MEANING

What does genus calamagrostis mean?