A sprinkler comprising a housing (22) fitted with an inlet port (26) connectable to a water supply line and extending into an inlet chamber (30), a hollow stem (44) member with an inlet end thereof being in flow communication with said inlet chamber and an outlet end thereof being in flow communication with an irrigation head (80), a diaphragm seal (32) sealingly fixed at peripheral boundaries thereof to the housing and sealingly articulated to the stem member and supporting it at an essentially upright position. The diaphragm is deformable between a first position in which the irrigation head is retracted within the housing and a second position in which the irrigation head projects from the housing. The sprinkler comprising at least one guard portion (510) adapted to prevent insects and undesirable material from entering the sprinkler housing during said second position.