Posted: 08/06/2014 at 21:11
moist atmosphere will be the cause. I cover my perennial seeds with grit and that helps avoid the moulds and the algaes.
Hardy perennials won't want it too hot and any that haven't germinated might do better outside. It would certainly help with the mould problem.
Hard to say whether it will do any harm but it could overwealm the seedlings as they come though and if it's too wet they might rot.
Which perennials are you growing?