To meet its urgent need for patrol and escort vessels, the British Admiralty decided to build a smaller ship, developed by naval engineer William Reed and based on a whaling boat design. The "Patrol Vessel - Whaler Type" could be constructed rapidly and in large numbers. Satisfied with the design but unhappy with the name, Sir Winston Churchill chose a shorter and more warlike name, the corvette, after a sailboat of old.

A corvette's shape and equipment being quite similar to that of a merchant ship, Canada was able to commission existing shipyards on the Atlantic or Pacific coasts, and along the St. Lawrence down to the Great Lakes, to build corvettes. Contracts were signed for the production of 64 corvettes in 1939-1940. The following years, 43 more were built by Canadian shipyards. They were called Flower class corvettes, as the first ones, supplied to the Royal Navy received flower names (Eyebright, Fennel, Hepatica). Later on, the Royal Canadian Navy (RCN) chose to give them names of Canadian cities (Chilliwack, Napanee, Saskatoon, Levis), although the term Flower class remained in use.
Throughout the war, corvettes were modified to improve detection systems and armament. The later Canadian-built Flower class corvettes benefited from those upgrades.

To serve aboard a corvette required unflinching courage and tenacity, as demonstrated by the glorious deeds of Canadian sailors escorting merchant convoys. The corvette remains the symbol of the Royal Canadian Navy's relentless fight against enemy submarines during WWII.

Nowadays there is only one Canadian corvette still maintained in her original state, HMCS Sackville.