Locate suitable plants for obtaining branches for the fence. Ocotillo are a protected species, so do not gather them from the wild. Instead, cut branches from a friend's plant or purchase them from a retailer. Select mature branches the length of the desired fence height plus 6 inches. Wearing gloves to protect against ocotillo thorns, use clippers to cut off desired branches. Take no more than half a plant's branches to minimize damage to the plant.
Fold three lengths of wire in half. Don gloves again. Place the wires around the first branch, spacing them evenly along the branch. Wrap each wire around the branch and twist its strands together once. Lay the second branch next to first, leaving enough room between them to allow for future growth. Wrap the wires around the second branch and twist each one again. Continue placing branches and twisting wire until the fence panel measures 5 to 6 feet. Make as many fence panels as required for total fence length.
Install posts about 3 feet apart along the fence line. If desired, place crossbars between posts for added strength.
Dig a 6-inch-deep trench immediately inside the fence line. Place the ends of the ocotillo branches into the trench; lash them onto the fence posts or crossbars.
Mix equal parts sand and soil. Fill the trench with the mixture. Water the fence thoroughly.
Continue to water the fence at least once a week. Spray the entire fence, not just at ground level. Eventually the ocotillo branches will take root and become a living fence.
Prune the fence once a year, during the dormant season, for an orderly-looking fence. Alternatively, leave the fence unpruned for a more natural appearance.