How to Build Above-Ground Planter Boxes
An above-ground planter box helps you maintain a neat, attractive and orderly garden. Constructed higher than the surrounding soil, the elevated planter or raised bed provides a solution to problems such as poor soil quality, soil compaction and poor drainage, while increasing overall crop yield. An above-ground planter box can be made from different materials, including landscape timbers, pressure-treated lumber, bricks and concrete blocks. You can easily assemble an above-ground planter built from landscape timbers.
Arrange two long and two short lengths of timbers in a rectangle over the selected spot in your yard or garden. Butt the corner of each length against the end of the other to form even joints.
Push the tip of a shovel into the turf along the outline of the rectangular timber bed to mark its boundaries. Also insert the shovel along the inner edges of the bed. Alternatively, spread chalk along the outer and inner edges. Remove the timbers and set them aside.
Roll up the grass within the marked outlines and use it to patch other parts of your yard. Excavate the ground between the outlines to a depth of 4 inches. Make sure that the trench runs level all around. Tamp the base to firm the soil and provide a secure foundation for the timbers.
Spread 1 inch of gravel in the excavation. Level the top, using a length of scrap lumber.
Drill 1/2-inch holes every 20 to 24 inches along the four landscape timbers. Lay the timbers over the gravel in the trench, making sure that the holes point upward.
Insert the tip of a 12-inch piece of rebar into each hole in the timber to anchor it into the ground. Pound the rebar with a sledgehammer until its tip is flush with the surrounding wood.
Arrange four more identical landscape timbers over the base course to add height to the planter box. However, position the lengths of this course counterclockwise to the previous one so their edges overlap in opposite directions.
Drill a galvanized timber screw through the corner of each length, and one through the middle, to join the timbers of the second course to the ones directly below. Depending on personal preference, leave the planter height as it is, or lay another course of landscape timbers to form a taller box.
Spread 2 inches of gravel over the base of the bed to improve drainage. Pour quality topsoil and compost or manure into the box until it's a few inches from the top. Level the top of the soil before setting out plants in the planter box.
Things You Will Need
- 6-inch by 6-inch landscape timbers
- Powdered chalk (optional)
- Scrap lumber
- Hand drill
- 1/2-inch bit
- Rebar, 12-inch lengths
- 10-inch timber screws
- Compost or manure
- Keep the above-ground planter box less than 4 feet wide so you can easily access plants growing in the middle from either side.