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Trimming – How it should, and should NOT be done!
  • Artistic Tree “As the twig is bent, so grows the tree.” This insightful old bromide about children might just as well serve as the cardinal principle for pruning trees. What you do to your tree in its first few years of life will affect its shape, strength, and even its life span. In importance, early pruning must rank just after selecting the right tree for the site and careful planting”.
    John Rosenow, Executive Director,
  • National Arbor Day Foundation
    It’s amazing the affect proper, or improper for that matter, pruning will have on a tree. At Robert’s Tree Service, we follow the pruning standards that were set forth by the International Society of Arboriculture, the foremost authority on proper tree care. In fact, we send only ISA Certified Arborists to evaluate your trees, and our tree trimmers have also received certification through the ISA. If you are going to hire a “professional” tree company to take care of your trees, make sure they are certified. Remember calling themselves “professionals” is not always an indication that they know what they’re doing! Following is some information about pruning – even if you plan on hiring a tree company to do the work it is always wise to arm yourself with some correct terminology and an idea of what the proper standards for the job are.

ArrowPruning Standards


  • Trees and woody plants respond in specific and predictable ways to pruning and other maintenance practices. Careful study of these responses has led to pruning practices which best preserve and enhance the beauty, structural integrity. and functional value of trees. In an effort to promote practices which encourage the preservation of tree structure and health, the W.C. ISA Certification Committee has established the following Standards of pruning for Certified Arborists. The Standards are presented as working guidelines, recognizing that trees are individually unique in form and structure, and that their pruning needs may not always fit strict rules. The Certified Arborist must take responsibility for special pruning practices that vary greatly from these Standards.
  • A. Crown Cleaning: or cleaning out is the removal or dead, dying, diseased, crowded, weakly attached, and low-vigor branches and watersprouts from a tree crown.
  • B. Crown Thinning: includes crown cleaning and the selective removal of branches to increase light penetration and air movement into the crown. Increased light and air stimulates and maintains interior foliage, which in turn improves branch taper and strength. Thinning reduces the wind-sail effect of the crown and the weight of heavy limbs.
  • C. Crown Reduction: is used to reduce the height and/or spread of a tree. Thinning cuts are most effective in maintaining the structural integrity and natural form of a tree and in delaying the time when it will need to be pruned again. The lateral to which a branch or trunk is cut should be at least 1/2 the diameter of the cut being made.
  • D. Crown Restoration: can improve the structure and appearance of trees that have been topped or severely pruned using heading cuts. One to three sprouts on main branch stubs should be selected to reform a more natural appearing crown. Selected vigorous sprouts may need to be thinned to a lateral, or even headed, to control length growth in order to ensure adequate attachment for the size of the sprout. Restoration may require several prunings over a number of years.
  • E. Crown Raising: removes the lower branches of the tree in order to provide clearance for buildings, vehicles, pedestrians, and vistas. When pruning for view, it is preferable to develop “windows” through the foliage of the tree, rather than to severely raise or reduce the crown.
  • II. SIZE OF PRUNING CUTS Each of the Types of Pruning can be done to different levels of detail or refinement. The removal of many small branches rather than a few large branches wil require more time, but will produce a less-pruned appearance, will force fewer watersprouts and will help to maintain the vitality and structure of the tree. Designating the maximum size (base diameter) that any occasional undesireable branch may be left within the tree crown, such as 1/2″, 1″, or 2″ branch diameter, will establish the degree of pruning desired.

Keys To Good Pruning
  • 1. Prune early in the life of the tree so pruning wounds are small and you can direct growth where you want it.
  • 2. Begin your visual inspection at the top of the tree and work downward.
  • 3. Identify the best leader and lateral branches (scaffold limbs) before you begin pruning and remove defective parts before pruning for appearance and form.
  • 4. Don’t worry about protecting pruning cuts. For aesthetics, you may feel better painting larger wounds with a nuetral-color tree paint, but the evidence is that it does not prevent or reduce decay.
  • 5. Keep your tools sharp. One-handed pruning shears with curved blades (secateurs) work best on young trees.
  • 6. Make safety a number one priority. For high branches use a pole pruner. Some, like the one pictured, have both a saw and shears on the same tool. A major job on a big tree should be done by a professional arborist.
  • 7. When you prune back to the trunk or a larger limb, branches too small to have formed a collar (swollen area at base) should be cut close. (Notice in the drawing of the pruning shears that the cutting blade is cutting upward for less effort and a close cut.) Otherwise, follow the rules of good pruning of larger limbs by cutting just outside the branch ridge and collar and at a slight down-and-outward angle (so as not to injure the collar).
  • 8. When simply shortening a small branch, make the cut at a lateral bud or another lateral branch (referred to as “head” or “headback pruning”). Favor a bud that will produce a branch that will grow in a desired direction (usually outward). The cut should be sharp and clean, and made at a slight angle about.

When to Prune
  • When you should prune depends to a large extent on why you prune. Light pruning and the removal of dead wood can be done anytime*. Otherwise, here are some guidelines, but recognize that individual species may differ.*Caution: In some areas of the country, diseases or insect occurence may be affected by the time of pruning. Check with your county extension agent or city forester; or an arborist or nursery operator to see if there are any local problems.

  • Pruning during dormancy is the most common practice. It results in a vigorous burst of new growth in the spring and should be used if that is the desired effect. It is usually best to wait until the coldest part of winter is passed. Some species, such as maples, walnuts, and birches may “bleed” when the sap begins to flow. This is not harmful and will cease when the tree leafs out.

  • To direct the growth by slowing the branches you don’t want; or to slow or “dwarf” the development of a tree or branch, pruning should be done soon after seasonal growth is complete. The reason for the slowing effect is that you reduce the total leaf surface, thereby reducing the amount of food manufactured and sent to the roots for their development and next year’s growth of the crown. Another reason to prune in the summer is for corrective purposes. Defective limbs can be seen more easily, or limbs that hand down too far under the weight of leaves.
  • FALL:

  • Because decay fungi spread their spores profusely in the fall and healing of wounds seems to be slower on fall cuts, this is a good time to leave your pruning tools in storage. This is the best time, however, to plant new trees. You might want to find some spectacular new additions to your landscape!

    If your purpose for pruning is to enhance flowering;

  • 1. For trees or shrubs that bloom in summer or fall on current year’s growth (e.g. crepe myrtle), prune in winter.
  • 2. For trees that bloom in spring from buds on one-year-old wood (e.g. dogwood and flowering fruit trees), prune when their flowers fade