Pruning mistakes may result in misshapen and weak ornamental trees. Shearing and topping are two of the most widespread and injurious pruning methods.
Shearing and topping are two methods of pruning flowering ornamental trees often used instead of more beneficial methods. Reasons for using shearing and topping may include:
- Lack of knowledge about tree growth and structure;
- Disinterest and poor information concerning proper equipment, and
- Time and anticipation of quick job turn around.
Shearing is cutting back terminal or tip ends of branches plants with hedge shears or power trimmers. This results in formal shapes and often-detrimental patterns such as spheres, rectangles or squares.
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Shearing usually results in such heavy top growth that there is no live growth under the canopy. Shearing in the wrong season also eliminates all or most of new flowers. Limit shearing to small–leaved plants appropriate for hedges or topiary maintained in formal gardens.
Topping is cutting back large upright branches between buds and nodes to reduce tree height, and tipping is cutting lateral branches between buds and nodes to reduce width.
These methods usually result in shoots, called epicormic, growing from buds developing from underneath a stem or branch, or in death of cut branches back to the next lateral branches. The epicormic sprouts weakly connect to the stems and branches and eventually decay.
Reduce Pruning Needs
The easiest way to avoid making pruning mistakes is to select proper plants for specific locations to reduce or eliminate pruning needs. Plant breeding advances and nursery industry selections provide wide assortments of plants that require little or no pruning. Avoid plants that:
- might grow too large for the site,
- are not reliably hardy, or
- become unsightly with age.
Pruning to Preserve Flower Buds
Trees and large shrubs that bloom after June usually form flower buds on shoots that grow the same spring. Prune these shrubs in later winter to promote vigorous spring shoot growth that supports plentiful and healthy flower buds. Examples of shrubs that bloom on current season’s growth include:
- Abelia X grandiflora (Glossy abelia)
- Buddleia davidii or B. globosa (Butterfly bush)
- Hibiscus syriacus (Shrub althea or Rose–of–Sharon)
- Hydrangea arborescens (Hills of Snow hydrangea)
- Hydrangea paniculata (Peegee hydrangea)
- Hypericum spp. (St. Johnswort)
- Lagerstromeia indica (Crapemyrtle)
- Stewartia species (Stewartia species)
- Vitex agnus–castus (Chaste tree)
Examples of shrubs that form buds immediately after bloom and flower on last season’s growth are:
- Cercis canadensis (Redbud tree)
- Chaenomeles japonica (Japanese quince)
- Chionanthus virginicus (Fringe tree)
- Cornus spp. (Dogwood species)
- Magnolia spp. (Magnolia species)
- Malus spp. (Crabapple species)
- Rapheolepis indica (Indian hawthorn)
- Rhododendron spp. (Azaleas and rhododendrons)
- Syringa spp. (Lilac species)
- Viburnum spp. (Several species of viburnum)
Inappropriate Shearing and Topping
Healthy pruning starts from inside the canopy near the tree trunk, working toward the outside of the crown. The procedure is simple:
- Remove all weak or dead stems up to the trunk or to a bud on a living healthy stem.
- Shape by removing or thinning out living twigs or branches by removing them
- at their points of origin on the parent stems,
- to a bud on a lateral side branch,
- to the “Y” of a branch junction, or
- at ground level.
The examples below may result, physiologically, in loss of vigorous healthy growth within the tree’s crown and, visually, to rigid shapes instead of the plant’s characteristic graceful shape.
- Shearing small trees so they look like formal lollipops reduces the distinctive flowering and graceful silhouettes of trees such as these Kousa dogwoods (Cornus kousa).
- “Dutch-boy haircuts”, a form of shearing along the growth tips of weeping branches, also diminish the valuable weeping qualities of ornamental trees like weeping cherries (Prunus spp.) and crabapples (Malus spp.). Cutting out excessively long weeping branches at the graft union can avoid the blunt “haircut look.”
- Recognizing and cutting out both crown and root graft suckers such as found in this weeping cherry (Prunus spp.) prevents misshapen trees and vigorous suckers from overtaking the desired weeping form.
- Pruning branch tips of small ornamental trees like red Japanese maples (Acer palmatum) directs branch growth into heavy amorphous structures reminiscent of cones and spheres. Ornamental trees used primarily as focal points need regular thinning out from main branches and the trunk to reveal their elegant fluid shapes.
Topping trees and its relate procedure, tipping, seem to be regional practices. Arborists and urban foresters concur in the program “Experts Agree: Don’t Top Your Trees” that topping is expensive, mutilating and obsolete.”
However, the practice still occurs due to myth and lack of public understanding about proper tree care.
In the southern United States, maples (Acer spp.) and crapemyrtles (Lagerstroemia indica) are two types of residential trees seriously ill-treated.
A dense rounded crown with epicormic sprouts along trunks and secondary branches and suckers from the base result from topping crapemyrtle trees. Healthier trees with enhanced branching and more blossoms result from regular thinning out procedures.