i have some propogators and sets of 40 cell trays to sit within them. if watering from the bottom, do i just put an inch or so of water inside the propogator tray, with the cell tray then plunged into it? the cells are about 1-1.5 inch deep.
You need to put enough water in to get the top of the compost damp, it will go darker. So you might put small amounts of water in, let it soak up and see if you need to add any more. If you put too much water in you'll have to tip it out.
I wouldn't put water in the propagator tray. I water by seeds by dunking in water but drain them off afterwards. Just shallow water, not enough to saturate
I agree with nut. I don't do that in practice though, I have a mister on my hose that I use for the first watering then I find the 'rain' setting on the hose is fine. What you want to avoid is adding so much water that it disturbs the seeds. How you achieve that is up to you but don't let the tray sit in water for more than a minute or two and drain it afterwards. By the way, it will drain more if you tip the tray to 45 degrees.