Prepare your heated propagator in the same way you would any other model. Sow your seeds, water well, and place the propagator on a window ledge or similar; switch it on, leaving the vents closed, only opening them to reduce excessive condensation. Once your seedlings appear, open the vents in the container lid to ensure adequate air reaches the plants – failure to do so can result in the growth of fungal and bacterial infections, which can easily wipe out your young charges. Once the seedlings are established, remove the lid and leave the tray on a sunny windowsill. After potting on your seedlings, gradually acclimatise them to cooler environments before moving them permanently.