Plant adult trees in front of the ugly structures you wish to conceal. You can purchase adult trees from nurseries that come already potted. Leave the matured tree in the pot or transfer the tree with its roots into the ground. For wider structures, you may need more than one tree to hide them. An alternative to planting adult trees is to plant hedges.
Decorate the backyard with potted plants and flowers. If you have random pipes in the yard, for instance, you can mask them by setting potted plants in front of them. Concrete slabs in the yard can be covered with potted plants so that you no longer see the concrete.
Set up a portable gazebo in front of the ugly structure. A portable gazebo can be purchased from a home and garden furniture store, and is simple to assemble. The posts and drapes from the gazebo can conceal the object behind it. Make sure you measure the dimensions of the backyard first before installing the portable gazebo, as gazebos can be large.
Build a brick structure around the ugly item you want to hide. Make a small wall to enclose the object with the bricks and grout. Build the wall high enough to conceal the thing you are hiding. Line the top of the brick wall with potted plants for decoration.
Plant vines on the unattractive structure. As the vines grow, they will wrap around the structure and conceal it with green leaves.