They'll root right through the mulch, as will most weed seeds. Depending on what kind of mulch you're using. Most fine textured materials like bark or compost or even gravel will allow seeds to sprout and roots to grow. If you're using a fabric or plastic or paper layer then seedling roots won't grow through that, but they will grow in whatever you put on top of the fabric layer.

Hey Chicken Lady, I'm glad you popped in to say hello. I had a great time up in Chicago meeting you and Buddy & the others. Hearing normal conversation consisting of latin names was a treat to my ears! Got your little blue fescue planted. I'm glad you handed it to me (my mom was thrilled !). Dax

Crocus does well in a lawn, as does aconite. I'm thinking that galanthus (snowdrop) would also do well, but I've never seen it tried and the flowers are rather plain. Winter aconite and snowdrop are some of the earliest flowers in the garden, usually flowering slightly before the early snow crocus. All are short enough that they'll tolerate being mowed--the leaves will simply stay up longer. But you'd never be able to blanket spray an herbicide while the bulbs are active as it'll damage or kill the flowers. The bulbs are active during the green leaf season, through April, and again in October through December. Hyacinth is a bit late and a bit tall for the lawn, plus the paddle-shaped leaves are definitely going to stand out as the lawn returns. But if that's your bliss, it's worth a shot. Grape hyacinth would be a possibility if you can hold off on mowing until after the flowers bloom, and it'd be rather striking. I use it throughout the gardens.

Depends on what you're planting. I do drop a light handful of mulch on larger seeded things like squash or beans, mostly just to keep the surface soil from becoming concrete when the sun heats up the damp soil. If I'm planting tiny seeds like lettuce or carrots, I usually just cover the seeds with a layer of bagged potting mix and water, water, water so that it doesn't dry out until they germinate. You could also put something like a board over them to keep the direct sun off until they germinate - slowing drying of the surface soil - just make sure you are checking them and pull it as soon as they come up. Once they germinate, I start slowly piling mulch around them as they grow.