For more success in propagating flats of coleus, shrub cuttings, and anything else you are rooting outdoors in the shade, monitor rainfall and irrigation closely. Just as overwatering kills more container plants than any pest, saturated soil can spell doom for vulnerable cuttings. Roots and root hairs can be easily overwhelmed when too much water in the soil deprives them of the oxygen they must have to grow. Set up a simple bench that will elevate the propagation area above ground level and allow the containers to drain. I use 2 cement blocks with 3 2×4’s laid across them, but then my style does run towards the utilitarian. However you do it, do it and keep a plastic drape handy, too. You can control the rooting medium and your watering habits, but may need to stave off a summer rainstorm to keep from overwatering cuttings.