Answer: Straw is essentially weed free although it may self seed a bit. It will work well but it needs to be applied very thickly for the entire season. In my garden it seems to work best if you cut open the bale and peel off slices or pads of it from the short end of the bale. Lay these out flat and touching at the edges, almost like tiles. This creates a very dense layer but it will rot down by the following spring. Hay will also work but usually has far more weeds than straw.
You can also use leaf mold which is made by chopping fallen autumn leaves and allowing them to rot until they reach a stage of being dark and crumbly, partially composted in other words. You could also used partly finished compost from your compost pile.
You can use almost any natural material for mulch. If it is applied thickly so it excludes light from reaching the soil, it should do the job. Smaller particles are preferred because they will break down and feed the soil faster. They are also easier to work into the soil when you are ready to replant with the next crop. However, you could also use very finely shredded or flaked bark if that is easier to find.
I hope this gives you some ideas.
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