Or, a white trillium flower proper.
(Glossary of Heraldic Terms)
The trillim is the floral emblem of the province of Ontario.
Originally HMS Minotaur, the cruiser commissioned into the RCN in April 1945 as Ontario. She wore pennant 53, and was finally decommissioned in October 1958.
"Ut incepit fidelis sic permanent" (Loyal she has been and remains so)
Green and gold
Badges Of The Canadian Navy by Arbuckle, J. Graeme. Halifax: Nimbus Publishing, 1987.