French Drains are designed to cover large areas and move lots of water. During a hard rain water will seep down through the gravel and into the Perforated French Drain Pipe that is buried under the gravel. The water fills into the pipe and moves down hill to the desired Exit Point. French Drains like the one in the picture above that are in the sun most of the day will have grass that overgrows the limestone. The gravel will disappear over time. The French Drain will continue to work even after the grass has grown over it. A "Thatch Filter " is made up of the grass that covers the French Drain. The French Drain then has two filters. First is the Neo-Prene Soc that comes around the Perforated French Drain Pipe. Later when the grass grows over it, the French Drain then has a second Thatch Filter. This ensures that the French Drain Pipe won't clog over time with dirt, sand, or debris. This only works with grass that does well in the sun like Bermuda or Tift.
Shade Grasses won't grow up and through French Drain gravel.
YOU DON'T WANT TO COVER THE FRENCH DRAIN WITH DIRT. IT WILL GREATLY REDUCE THE DRAINAGE PERFORMANCE OF THE FRENCH DRAIN. IT DEFEATS THE ENTIRE REASON FOR THE FRENCH DRAIN. IF YOU DON'T LIKE THE WAY IT LOOKS AND CAN'T BE PATIENT ENOUGH TO WAIT UNTIL THE GRASS GROWS THROUGH IT IF IT IS IN THE SUN, THEN DON'T INSTALL IT AT ALL.
IF THE FRENCH DRAIN IS INSTALLED IN THE SHADE YOU CAN USE DECORATIVE ROCK TO MAKE A FOOT PATH OR ROCK GARDEN ON TOP OF IT. YOU ARE ONLY LIMITED BY YOU IMAGINATION.