Time evolution of the growth barriers. The plotting style corresponds to Fig. 1: the yellow region corresponds to the fragmentation barrier while the grey region indicates the drift regime. The red and blue horizontal lines denote sizes corresponding to the Stokes number of unity and 10^-2, respectively. The purple line shows the maximum size of dust aggregates, which generally follows the growth barriers, except for the earliest stages of evolution, when it is restricted by the growth timescale. The radial drift barrier gains significance as the dust-to-gas ratio decreases during the evolution.