the planters are 5 1/2 inches deep and 6 inches wide ... and 3 feet long. I put some old potting soil with styrofoam bubbles (from old house plants) on the bottom for about 2 inches, then i put 1 inch of new potting soil above it and place a variety of snapdragon, bachelor buttons, marigolds, and a wild flower mix throughout the planters, and covered all seeds with another 1/2 to 1 inch of new soil and watered carefully untill completely saturated. .... the question .....I have about 2 1/2 + inches of space from the top edge of the planter to the soil inside... is this too deep? should the soil surface be closer to the top of the planter?