To "clean" a tree or bush is to prune it to maintain its health. When you clean a gardenia bush, you remove all of the branches and twigs that are detrimental to the well-being of the bush. Gardenia bushes should be cleaned at least once a year, in the summer, just after they finish blooming, to stimulate new growth. Contrary to popular belief, this will not cut down on next year's growth. In fact, your gardenia will fill out and bloom more vigorously on the new wood it produces after the old wood is gone.
Prune diseased or infested branches. Do not leave these branches until summer. As soon as you notice signs of infection, prune the branch back to just above the first healthy node (the point that branches off to become a twig) that is at least 2 inches into healthy plant tissue.
Prune any dead, dying and underproducing branches. Prune secondary branches back to the main branch and prune main branches down to ground level.
Prune any thin, spindly branches and any branches that rub against their neighbors. Stand back from the gardenia bush and identify these branches by painting them with nail polish or tying a string around them. Then go in and prune them to the ground or back to the main branch.
Cut your gardenia bush down to size. Use your pruning shears to cut the branches back to just above the node that is nearest the desired height of that branch.
Wipe your pruning shears down with alcohol after each cut. This will avoid the spread of disease.