Native rock planters provide raised growing areas for plants, and include the benefit of better soil drainage, as well as the aesthetics of varying height and a natural look. Before beginning, take your little one with you to look for stones to use in construction, turning the project into a treasure hunt that makes him feel included. Once the rocks are gathered, you must decide where to build. Whether you construct the rock planters close your your house, or out in the surrounding landscaping, these planters are not movable, so short of tearing them down, where you put them is where they will stay.
Outline the area for the rock planter. If you are creating a curved planter, then use spray paint to mark the location. If you prefer straight lines, use wood stakes and string to create more defined limits.
Dig out any plants or mulch within the planter area. If you are installing the planter in a grassy spot, dig out the grass and use it to fill in bare spots in other parts of your lawn.
Make a trench with a straight blade shovel, following the outline of the planter. The width of the trench depends on the size of the native rocks. Dig down 6 inches, maintaining flat trench walls.
Fill the trench with 4 inches of gravel. Pack the gravel down with your foot to firm up the planter foundation.
Mix a batch of mortar in a large bucket, following the package directions. When properly mixed, mortar has a consistency similar to thick mud.
Add a single layer of native stones on top of the gravel. Depending on the rocks, you may be dealing with evenly cut stones or more natural rocks with varying thicknesses. If they are even, then check the rocks to ensure they are level with each other. Add or remove gravel under them if necessary. For more natural rocks that are not cut evenly, you will need to select stones that are similar in height. Future rows will require the same sort of selection process. You may also build the rows similar to a puzzle, selecting different-sized stones and placing them together to equal the height of the stone next to them in the row. For a smoother wall surface when working with uneven rocks, select rocks that have one side edge that is fairly flat. Place the flat edge toward the outside of the planter to create a somewhat smooth wall. If you prefer a rough natural wall, place the jagged edges outward. Try to keep the jagged edges in line with each other as you set them in place, so they do not stick out too far and cause a hazard for someone walking by. Use your eye to gauge and adjust the rocks.
Spread 1/2 inch of mortar on the ends of the stones as you place them on top of the gravel. Use a masonry trowel.
Place a second row of native stones on top of the first. Spread a 1/2 inch-thick layer of mortar on top of the first row of stones, and then place a second row of stones on top in the same manner as the first. To create a sturdy planter, have the second row of rocks straddle the gaps between the first row, similar to laying bricks. Repeat the process with a third and forth row if desired. Maintain a height of 3 feet or shorter to ensure you are able to easily plant and care for the vegetation.
Stagger rocks at the corners if your planter has them. At each corner, alternate which row of rocks ends at the corner, and which butts up against the rock that forms the corner, as you would with the corner of a brick wall. This alternating pattern joins the two sides of the planter together, making it sturdier. Let the planter walls dry for a day to cure the mortar.
Break up the soil along the ground inside the planter. Use a hoe or hand tiller to loosen it up.
Line the inside of the planter walls and ground with a layer of polyurethane. This protects the walls from excess moisture that might damage the mortar between the rocks.
Poke multiple holes all over the bottom of the plastic sheeting to allow excess water to drain into the ground.
Fill the planter with a 50/50 mixture of soil and peat. Add the mix to within 4 inches of the top of the planter. Add desired vegetation to the planter, and cover with 3 inches of mulch.