This image was taken in my driveway area. The river gravel rocks (poly pebbles) are dispersed in a space that will hold up to nine cars. I decided to take a picture of these clustered rocks because I added a textures category to this site.
The various colors of rocks clumped together require routine maintenance because we have a large oak tree off to one side of the driveway. About three times per month I have to blow the leaves off of the driveway and also I spray the weeds that push through.
The best weed and grass killer for killing plant growth in river rocked areas is Spectracide.