Does it look like an aster? Don't be fooled, it's a different genus entirely.

This common flower of the summer months can be found throughout Southern Ontario. Called the Daisy fleabane (Erigeron annuus), it can grow as a perennial or biennial. The flower heads are white with yellow centres and this species generally grows on dry sites and open fields as well as tolerating a wide variety of soil conditions like sand and clay.

This plant isn't to be confused with the Oxeye Daisy, which looks like this: