We present and analyze a multirate fixed stress split iterative coupling scheme for coupling flow and geomechanics in a poroelastic medium involving fracture propagation modeled with a phase field approach. The novelty of this work lies in the efficient integration of the fixed-stress split coupling scheme with phase-field fracture propagation models. The multirate coupling algorithm utilizes different time-scales of the flow and mechanics problems, by allowing for multiple finer time steps for flow within one coarse mechanics time step. When applied to production scenarios, the multirate scheme results in massive reductions in the number of mechanics linear iterations, without jeopardizing the accuracy of the obtained results. A number of numerical simulations substantiate our algorithmic developments. These tests include prototype computations, multiple propagating fractures, and fractures initialized by a microseismic probability map.