Tree pruning involves the removal of live branches, as well as dead, diseased, and damaged branches for the health of the tree, while tree trimming only involves the removal of branches that interfere in some way.
Typically, trimming is removing overgrown branches from crops such as trees, shrubs, and hedges. In this case, tree trimming only relates to trees. Extreme growth can prevent sunlight exposure to most parts of the tree hence inhibiting growth.
ALWAYS prune back to or just above a growing point (branch or bud) or to the soil line. NEVER leave a stem or branch stub. NEVER top a tree to “rejuvenate” growth.
The two basic types of pruning cuts are heading and thinning. Thinning cuts are the least invigorating type of cut and are the most effective pruning cut for maintaining woody plants in their natural form. Pruning, particularly heading cuts, stimulates regrowth very close to the pruning cut.
Overgrown trees can pose a serious risk to your property and your family. Dead or damaged branches can fall and cause damage to your home or car or even injure someone. In addition, overgrown trees can block sunlight and views and can even damage foundations or driveways.
Let's discuss the importance of pruning. While a tree will not directly die from a lack of pruning, neglecting the structure of a tree can impact its long-term health. Lack of pruning in a tree can lead to structural defects. These structural defects can result in significant portions of a tree failing.
The cut is the key to good pruning. As a rule, always cut back to a branch, twig or bud that is pointed in the direction you want the tree to grow. This method encourages controlled, healthy new growth. If you're unsure whether to remove a branch, don't cut.
The 1/3 rule involves cutting about 1/3 of wood during any pruning activity. This moderate pruning practice is a balanced approach to thinning out shrubs to stimulate new growth. The plant loses a good amount of stems, usually on the top section, allowing more light and air to enter the inside of the plant.
An improper cut like a flush cut (cutting too close to the trunk) or a stub cut (cutting too far from the trunk) can cause irreversible damage to a tree. A flush cut removes the branch collar and leaves a large wound in the side of the tree that won't heal properly.
Municipalities and homeowners often remove the lower limbs for pedestrian and vehicular clearance or to let the sun shine in for grass to grow. Mature trees, especially evergreens, benefit when healthy lower branches are left intact. Removing large limbs can increase the risk of decay.
Branches that Double-cross or Grow Inward or Grow Downward:
Similarly, branches that grow inward toward the central stem or trunk are likely to end up chafing against other parts of the plant, so it's best to prune them.
The ISA guide to tree trimming (they use the term “pruning”) covers the basics of how to properly maintain mature trees.
There is never a bad time to remove dead, damaged or diseased branches. But most trees benefit from pruning in mid to late winter. Pruning during dormancy encourages new growth as soon as the weather begins to warm. The lack of leaves after autumn allows you to easily identify branches and limbs requiring removal.
Synonyms of pruning (noun shearing) clipping. cropping. shortening.
RULE 1: Prune your block with the weakest trees first and your strongest trees last. Trees that are pruned in early winter become more vigorous than trees that have been pruned just before or after flowering.
In pruning, there are three primary types of pruning cuts, thinning cuts, reduction cuts, and heading cuts, each giving different results in growth and appearance.
The node is where leaves, buds and shoots emerge from the stem. You should always cut just above a node, as this prevents 'die back' and therefore disease. Also, by cutting above a node you can manipulate new stems, leaves or flowers to form in a desired direction, as nodes form on different sides of a stem.
After a tree is topped, it grows back rapidly in an attempt to replace its missing leaves. Leaves are needed to manufacture food for the tree. Without new leaves, the tree will die. The new branches that sprout up below the cuts will continue to grow quickly until they reach the same size it was before it was topped.
Without leaves, the cut tree cannot produce food for the growth of its roots. However, the roots might have enough nutrients left to allow the growth of sprouts from the roots or from the leftover stump. If a sprout develops enough leaves, it can eventually grow back into a tree.
Late summer or early fall pruning causes vigorous re-growth of tissue, which in some cases may not harden off by the time winter arrives, leading to possible cold damage to the new growth.
The General Pruning Timeline for Healthy Trees
But in general, most arborists will suggest the following: Mature Trees—Should be pruned or trimmed every 3-5 years. Juvenile Trees—Should be pruned or trimmed every 2-3 years.
Depending on its size, age, and condition, no more than 5% to 20% of a tree's crown should be removed at one time. The main reason for this is to avoid the tree's stress response of producing lots of suckering branches that are weak and may develop in the wrong places in a tree's crown or along its trunk.
The best time to prune is after flowering. If the plant needs to be renovated, or severely reduced, this can be done late winter and early spring just before growth begins. Remove old flowers (deadhead) and cut back to healthy outward facing buds. Remove damaged, diseased, old wood and straggly growth.