A native of Southeast Asia, elephant ear is hardy in U.S. Department of Agriculture (USDA) plant hardiness zones 8 through 11. In USDA zones 8 through 9, elephant ear usually dies to the ground, returning in spring once soil temperatures warm. In USDA zones 10 through 11, the plant is nearly an evergreen, according to the Floridata website. Partial shade is ideal for the plant, though with enough water it withstands full sunlight.
In your case my guess is your fence posts were taller than the fence, so your wood fence posts should be in the ground at least 3 feet. When it is time to install the fence post, be sure it is in line with the other posts and it is plumb.It is also important that the fence post is centered in the hole.Start to add the crushed gravel in 5-inch lifts.our fence posts have a tremendous amount of force against them each time the wind blows. You may not think a 5-foot-tall fence is high, but in terms of wind load, it is substantial. To get an idea of what I am talking about, lift a 4x8 sheet of plywood up and take it outdoors on a windy day.
If you have time, start the holes one day, fill them with water and come back to remove the much softened soil the next day. Measure and mark the location of each fence post. Post hole diggers have a maximum effective depth of about 3/4 of their handle length, so a five foot pair will dig about 3 1/2 half deep. Very hard earth like clay is extremely difficult to dig with a manual pair of post hole diggers.