The best time to prune is when the coldest part of winter has passed. Now is the time to remove dead and interfering branches. A tree is a photosynthetic factory that can be fine-tuned for efficiency by encouraging an even spacing of branches throughout the crown. If a branch is densely shaded, it may not contribute as much energy to the tree as much as the energy it takes to remain alive. Remove branches that are weak or shaded by healthier, more vigorous branches.
Another important factor to consider is how the branch is attached to the trunk. Narrow crotch angles may become structurally weak if bark is included or pinched as the branches grow thicker each year. Branch angles between 45 and 90 degrees are strongest and resist storm damage.
Finally, increasing air circulation throughout the crown will decrease the time that the leaves remain wet after a rainfall. Decreasing the humidity can reduce the amount of fungus that can grow on the foliage. Thinning the crown can reduce the need for pesticide use to control leaf spot and scab diseases.
Formative and preventative pruning can ensure a long and healthy life for your trees as they produce oxygen and filter the air you breathe. They are the backbone of our landscape, making our lives so much better as they frame the view of our outdoor world. This is the very best time to prune, now that winter’s back is broken and spring is on the way.
MAKING THE CUT
When removing a live branch, pruning cuts should be made just outside the branch bark ridge and collar (Figure 3). This location of cut is in contrast to a “flush cut” which is made inside the branch bark ridge and collar. Flush cuts should be avoided because they result in a larger wound and expose trunk tissues to the possibility of decay. If no collar is visible, the angle of the cut should approximate the angle formed by the branch ridge and the truck.
When removing a dead branch, the final cut should be made outside the branch bark ridge and the collar of live callus or woundwood tissue. If the collar has grown out along the branch stub, only the dead stub should be removed; the live collar should remain intact (Figure 4).
If it is necessary to reduce the length of a branch or the height of a leader, the final cut should be made just beyond (without violating) the branch bark ridge of the branch being cut to. The remaining branch should be no less than ⅓ (one third) the diameter of the branch being removed, and with enough foliage to assume the terminal role. On large trees this type of cut is commonly called drop crotching (Figure 1).
Figure 3. Pruning cuts should be made just outside the branch bark ridge (top of cut) and the collar (bottom of cut).
Figure 4. On a dead branch that has a collar of live wood, the final cut should be just beyond the outer edge of the collar.
Figrure 5. Remove a large limb by making three cuts. First cut on the bottom of the limb about 12 inches (30cm) from the branch attachment (left). Make the second cut on the top about 1 inch (2.3 cm) from the under cut. The final cut is just outside the branch bark ride and the outer portion of the collar (right).
Renewal pruning is the annual or semi-annual removal of a shrub’s older stems to ground level. This exposes the more productive young stems to full sunshine, while controlling the plant’s ultimate height. First, determine the natural look or growth habit of the shrub to be pruned. Then determine the ages and remove the older or damaged limbs. Place your loppers as low as possible on each older limb and cut. Remove all of the older stems possible without damaging the plant or causing it to look out of balance.
Renewal pruning not only removes older libs but it also lowers the shrub’s height. When this pruning method is used with the heading back pruning technique, the shrub can be reduced drastically without destroying its natural appearance.
After renewal pruning, the remaining branches may be too tall and limber. Head back by cutting at the nearest limb to the height desired. Cut as near to the side branch as possible and at the same angle as the limb.
TIPS ON PRUNING HEDGES
Prune hedges wider at the bottom than at the top. This allows light to fall directly onto the lower foliage, keeping it actively growing and replacing the older leaves.
New growth starts at or near the cuts and forms a solid cover of new growth. Each time you shear a hedge, leave ½ to 1 inch of previous growth—the shrub needs this new growth to keep the plant healthy with the ability for regrowth.
Rejuvenation pruning is the cutting back of all stems to a height of 4-10”. This technique is used to revitalize multiple stems, leggy overgrown or diseased shrubs. It is particularly appropriate on the following shrubs: Butterfly bush, Dwarf Bush honeysuckle, Hibiscus, Hydrangea Annabelle, Potentilla, Spirea (except Bridal wreath and Snowmound).