"Professor ... Weasley's mutilating my roots, sir."
"Change roots with Malfoy, Weasley....Now"
-- Draco and Professor Snape over Ron's daisy-chopping technique (PA7)
The daisy is a mundane flowering plant used in potions.
The roots of the daisy are used in a shrinking solution. Ron is told to help the injured Draco Malfoy by chopping his daisy roots, but Ron does them so unevenly that Professor Snape makes them swap roots (PA7).
An old wives’ tale says that daisy roots, boiled in milk and fed to a farm animal, can stop the animal from growing too large.
Daisy roots are used in Shrinking Solution in Third Year Potions. The Pottermore version of Shrinking Solution also includes Daisy Roots.