[a] The third batch of twelve ships to be ordered in May 1915, they differed from the preceding Acacia class only in mounting a heavier armament.

[1] However, they also acted as dispatch vessels or carrying out towing operations, but as the war continued and the threat from German submarines grew, became increasingly involved in anti-submarine duties.

[1] The sloops were designed to be armed with two single-mounted QF 4.7-inch (120 mm) low-angle guns as protection against German raids on the minesweeping flotillas.

[1] The Azaleas were ordered in May 1915 as part of the War Emergency Programme and entered service between September and December 1915.

Recommissioned on 9 August 1917 as Q10 and using the name Dolcis Jessop, the vessel had a short career as it was sunk in a collision with the German U-boat, SM U-151 off Casablanca on 2 October.

Another, Myrtle, was mined in 1919 during Royal Navy operations in the Baltic Sea as part of the Allied intervention in the Russian Civil War.

[8] On 28 September 1943 she was sailing from Cephalonia to Greece with 840 Italian prisoners of war when Ardena struck a mine and sank.

[8] Zinnia was transferred to Belgium on 19 April 1920 and used for fishery protection duties by the new Royal Belgian Navy.