Is there a fungus among us?
This look like a Fuligo species of Myxomycete, a slime mold. It won't hurt the plants. You can rake it or spray it with a hose and it should wash away. Or you can let it be - it will change color and even seem to move a bit over the next few days, then when conditions dry out, it will also dry up and sort of disappear, leaving behind a lot of spores that will wait for the right conditions. Learn more here about a similar slime mold:http://plantclinic.cornell.edu/factsheets/slimemolds.pdf