I'm wondering why instructions for wheatgrass-growing always say to keep the grains covered (e.g. with newspaper) for the first few days after planting.

My first attempt at wheatgrass just came to a very mouldy end (I know a little mould on wheatgrass can be harmless, but there was really a lot, and my boyfriend insisted I throw it all away), and I think the lack of air circulation while the wheat was covered was at least partly responsible for the mould growth.

I've just planted new batch today, and I'm keeping it uncovered - should this work? I've also added a little vinegar to the water I use to spray the grains.