Answer: Black plastic is not recommended around plants because it keeps both air and water from reaching into the soil.
Newspaper or a layer of cardboard will work for a certain period of time to prevent weeds from germinating, but eventually it will rot away and need to be replaced.
Some gardeners use a weed barrier fabric under gravel, it is specially made to be porous. While it will stop weeds from growing up through it, it will not stop seeds from germinating in the surface gravel. (Neither will newspaper.)
The gravel combined with bits of leaves and so on that work their way into the gravel make a perfect germination bed. The gravel can be raked periodically to disturb the seeds that land in it, or the area can be treated with a pre-emergent herbicide. Corn gluten or a commercially formulated product may be used.
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