Gather large rocks that have a smooth surface, are 6 to 8 inches long, and are flat. Brush the entire surface of each rock to make sure there is no dirt or residue left on the rock. You need a clean surface for the paint to adhere.
Paint the entire top and sides of the rock with acrylic paint, any color you like, according to Home Made Simple. There's no need to paint the bottom. Let it dry. Do several at a time in different base colors.
Write the plants' names on the rocks with a permanent marker in fancy letters. Get different colors of markers to use on different colors of base paint. Put garden phrases on some of the rocks. Draw of some of them. Let the permanent marker dry.
Spray the finished rocks with a spray sealer for stone floors. This will protect them from the elements. Enjoy your plant markers and garden art.