Sujit asked, >What is the importance of putting a thin layer of coarse grit? I see that >im many of the photos posted. It keeps the surface of the soil from drying out too fast and keeps it from forming an impervious layer, which can be a problem if the mix contains peat and it gets dry. It also keeps the seeds from washing around when watered overhead. The best sort of grit is granite, but many people use aquarium gravel, which is more widely available, and I sometimes use plain pumice if I don't have any grantie grit on hand. My preferred seed mix has always been 2 parts coarse, sharp sand, 1 part pumice, and 1 part sphagnum peat, but that type of sand is not available everywhere, so some other kind of grit could be substituted rather than use the kind of fine, eroded sand found in the lower parts of rivers and near beaches. People who can't get pumice usually use Perlite instead, but it is inferior to pumice in every respect except weight (a large flat of 4-inch pots with my mixes is pretty heavy). Jane McGary Portland, Oregon. USA