From the

                            From the American National Standards Institute  (ANSI)

                        Accepted from the

1) International Society of Arboriculture (ISA

2) Tree Care Industry Association formally the National Arborist Association

3) The court system

4) Around the world

ANSI A300-1995 for Tree Care Operations-Tree, Shrub and other Woody Plant Maintenance

Standard Practices

Section 5.3 Mature Tree Pruning

5.3.1 General

The following specifications should be used with pruning objectives.

5.3.1.1 Pruning cuts shall be made in accordance with 5.2.5.

5.3.1.2 Tree branches shall be removed in such a manner so as not to cause damage to other parts of the tree or to other plants or property. Branches too large to support

with one hand shall be precut to avoid splitting or tearing of the bark. (See figure 1) Where necessary, ropes or other equipment should be used to lower large branches or

portions of branches to the ground.

5.3.1.3 When a branch is cut back to a lateral, not more than one-fourth of its leaf surface should be removed. The lateral remaining should be large enough to assume the

terminal role.

5.3.1.4 Not more than one-fourth of the foliage on a mature tree should be removed in a growing season.

5.3.1.5 Upon completion of pruning a  mature tree, one-half of the foliage should remain evenly distributed in the lower two-thirds of the crown and individual limbs.

5.3.2 Size Specifications

A minimum or maximum diameter of branches to be removed should be specified to establish the extent of pruning, such as: the removal of branches 3 in (7.5 cm) in diameter

and greater, or; the removal of branches 2 in (5cm)  in diameter and greater. Ect.

5.3.3.1 Hazard reduction pruning

Hazard reduction pruning is recommended when the primary objective is to reduce the danger to a specific target caused by visibly defined hazards in a tree. Hazard reduction pruning should consist of one or more of the maintenance pruning types.

5.3.3.2 Maintenance pruning

Maintenance pruning is recommended when the primary objective is to maintain or improve tree health and structure, and includes hazard reduction pruning. Maintenance

pruning should consist of one or more of the following pruning types:

a)       Crown cleaning: Crown cleaning shall consist of the selective removal of one or more of the following items: dead, dying, diseased, weak branches and waters prouts

from a tree’s crown;

b)       Crown thinning; Crown thinning shall consist of the selective removal of branches to increase light penetration, air movement, and reduce weight:

c)       Crown raising: Crown raising shall consist of the removal of the lower branches of a tree in order to provide clearance;

d)       Crown reduction (crown shaping): Crown reduction reduces the height and/or spread of a tree. Consideration should be given to the ability of a species to sustain this type of pruning;

e)       Vista pruning: Vista pruning is selective thinning of framework limbs or specific areas of the crown to allow a specific view of an object from a predetermined point;

f)        Crown restoration: Crown restoration pruning should improve the structure, form, and appearance of trees that have been severely headed, vandalized, or storm damaged.

5.4.1 At Planting

When a young tree is planted, dead, broken, and split branches should be removed. A central trunk or well – spaced multiple trunks or leaders (as most appropriate for the species and specimen) should be developed by removing competing leaders and removing, heading, or thinning laterals on vigorously growing branches that compete with the selected leader(s). Branches should be retained on the lower trunk to increase taper.

5.4.2 During the first three years after planting

A strong scaffold branch structure be developed by selecting the primary scaffold branches. To improve the scaffold structure, branches that are crossing, have included bark, or interfere with the scaffold branches should be removed. Scaffold branches should be properly spaced. For deciduous shade trees that will reach or exceed 40 ft (12m) in height at maturity, the recommended spacing between primary scaffold branches is approximately 18 in (46cm). For smaller species, 6 to 8 in (15 to 20cm) would be adequate.

5.4.3 Between four and six years after planting

The development of a good, structurally sound scaffold branch system should be continued by selective thinning of or on branches and removing dead, interfering , split, and broken branches. Large-growing branches with narrow angles of attachment shall be removed from the trunk or canopy. Lower branches shall be pruned (crown raising) so as  not to interfere with human needs where appropriate.

Also included in ANSI standards is definitions, other types of pruning, and safety procedure for tree care operations: