Step 1: Fill Pot to the Brim
Fill the container to the brim with potting mix. Tap it lightly on the work surface to settle the contents, and level off any excess. Firm to 1⁄2 in (1 cm) below the rim to eliminate air pockets. Use a presser of wood or plywood or the base of another pot.
Step 2: Sprinkle Seeds
Pour some of the seeds into the palm of one hand, and use finger and thumb of the other to sprinkle them over the surface. Never sow direct from the packet, as it is hard to shake seed out evenly, and seedlings are likely to end up in overcrowded patches.
Step 3: Soil Over Seeds
Sift a shallow layer of soil over the seeds if they need darkness for germination. Fine seeds needing light, such as begonias, can be pressed gently into the surface or covered with a thin layer of vermiculite. Label with the variety and date of sowing.
Step 4: Water from Below
Water from below by standing the pot in shallow water until moist patches appear at the surface. Drain and cover with a clear polythene bag, or enclose in a propagator. Keep at the recommended temperature and out of direct sun; cold nights or very hot days can cause failure.
Seedlings in trays become overcrowded quickly, leading to weak growth. To avoid this, “prick out” seedlings when they are large enough.