I do not try to mulch some things that are small or planted close together, (radishes, carrots etc.) it is just too tedious for me, however everything else that I grow, I mulch and they all do fine.

I think that all mulch does is to repress unwanted grass and weeds by blocking the light out, conserve moisture and keep soil temperatures at a more consistent level. I do not see any of that as harming any plants.

Another plus is that usually by late summer / early fall most of the mulch has broke down and added back other material to the soil, and is not there in the way of my planting a fall crop of greens.
That is just my .02
Bill P.

Depends on the type of mulch. Oak leaves can be huge depending on the type of oak. If you can shred them, I'd definitely use them anywhere you wish. As Bill says, the benefits are numerous. And for smaller seedlings, finer mulch (shredded leaves) are perfect because they can be sprinkled lightly over everything and you can use your hand to skim the tops of the seedlings so the mulch settles in between.

Thanks Bill and violet!

I would only remind you of the obvious - don't put it over planted seeds or they'll have a harder time breaking out (or they won't at all). Don't put around new seedlings, because it might cause damping off.

I have shredded oak leaf mulch around my tomatoes, peas, zucchini, onions, marigolds, nasturtiums and peppers. Within a few days I intend to get it around my corn and pole beans, but I want to weed first.

We have 2 big oak trees and I used last fall's leaves as the main "brown" in my lasagna raised beds, along with horse manure. Everything is growing well, so other than the caveats above, it should be just fine.

It is entirely possible to mulch seeds and seedlings, and necessary to keep the ground moist when planting in August 100F degree temps for a fall planting. So long as the mulch is fine and light and it's just a thin layer to shade the ground, the seedlings will come up just fine.