My experience with growing mulch was to wait until a nearby swamp had
frozen over. Then, with scythe in hand, I mowed the tall swamp grass.
Swamp grass was an ideal mulch because (undispersed) seeds of swamp grass
wouldn't grow on upland soil, rainwater passed through it and it lasted a
bit longer than straw or hay. I spread it before the snows came. When it
became to plant the garden, the mulch was pulled aside to form rows. Once
the plants were up, the pulled-aside mulch was pressed against the plants to
prevent weeds from emerging.