Large-diameter PVC pipes (2 inches and larger) are good choices for garden projects that require a sturdy structure. You can create the structures by joining the pipes together with connectors, or you can drill through the pipes and insert smaller pipes through the openings. PVC pipe structures are both lightweight and sturdy. Paint them with acrylics or latex paint to camouflage the construction material and create decorative designs in your garden.
Build a chunky fence around a vegetable garden or around the border of your property with large-diameter PVC pipe. The large pipes make strong posts every 3 to 4 feet around the garden. Drill holes and thread smaller PVC pipes through the larger pipes to create rails for the fence.
Large-diameter PVC pipes may be used to build a garden arbor. A ladder-style design on both sides with a crosspiece at the top is an attractive arbor to place at the entrance to a garden or to stand as a focal point in the yard.
Large-diameter pipes make a good vertical support system for a trellis in the garden. You can build the crosspieces of the trellis with smaller PVC pipe or wire, depending on the type of trellis you need. Horizontal wires between the posts will support trailing blackberry vines, but you may wish to use 1-inch diameter PVC pipe to support grape vines. A PVC pipe trellis may also be decorative with horizontal PVC pipes running in a pattern between the large-diameter pipes.
Another garden project you can make with both large- and small-diameter PVC pipe is a frame for a gazebo. The large-diameter pipes are the main vertical support structures for the walls and the roof. The smaller pipes can fill in horizontally between the vertical supports. Kits and plans to make PVC gazebos are available from online retailers. (See Resources for free plans.)
The corners and primary wall supports for a greenhouse may be constructed with large-diameter PVC pipe. You can also use the large pipes as the horizontal cross supports in the wall structure. You can purchase plans online for a PVC greenhouse. (See Resources for free plans.)