The famous opening "蒹葭苍苍" describes reeds growing thick and gray-green by the water.
Tips
history
葭 is not used in everyday modern Chinese; the ordinary word for reed is 芦苇. It is famous from the Book of Songs line quoted, and from 葭莩 (the thin membrane in a reed; figuratively a distant relative). It is the grass radical 艹 over 叚 for the sound.
register
Classical and literary — confined to old poetry and the bound word 葭莩, not modern speech.