Q. I have a small garden with white marble rocks between the plants. I understand there is something which can be put down on the ground before laying the marble chips to prevent weeds from growing up between the rocks. I'm willing to remove the marble chips if necessary to do whatever it takes to keep the weeds out of the bed. Weeding the mulch is a difficult process. I've heard that laying newspaper or plastic down will keep weeds from growing but with plastic bags I would be concerned about water absorption and runoff.
—M.L., Washington, MD
A. 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; a porous material, it allows both air and water circulation. Although it will stop weeds from growing up through it from the soil surface below, it will not stop seeds from germinating in the gravel. (Neither will newspaper or cardboard.)
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.
—National Gardening Association
