Unlike children who grow up too fast, the bristlecone pine (Pinus aristata) stays the same size for years. Eventually the coniferous evergreen tree grows to about 20 feet tall, but you may never see it grow past 6 or 8 feet in height. The good news is that this slow growth makes pruning a rare task. In fact, bristlecone pines do better with pruning kept to removal of dead or diseased branches. Bristlecone pine trees grow in U.S. Department of Agriculture plant hardiness zones 4 through 7, and thrive in full sun and well-draining soil.
Remove dead, needleless branches any time of year. Cut with pruning shears or a pruning saw at the base of the dead branch. Make the cut just outside the branch collar where the branch joins the trunk or a larger branch. Do not leave a stump, but do not cut into the bark of the connecting wood.
Prune out limbs infected with pine blister rust. Infected limbs have cankers -- swollen, discolored areas on the branches. If the canker is less than 4 feet from the trunk, remove the entire branch at the branch collar. If the canker is more than 4 feet from the trunk, cut into healthy wood at least 12 inches from the canker, as long as you are still within the needled part of the branch. If this would mean that no needles are left on the branch, remove the whole branch. Disinfect pruning tools between cuts and before using the tools on another plant or tree to avoid spreading the pine blister rust to uninfected limbs.
Trim only new growth at the tips of branches if you need to cut back a branch that sticks out. Keep pruning for shape to a minimum, and do your trimming between the middle of June to the middle of July.