Crown thinning and raising

Crown thinning and raising

Crown Thinning Techniques and Best Practices

Crown thinning and raising are essential tree pruning practices that improve a tree's health, structure, and aesthetics. While both focus on removing branches, they achieve different goals and require distinct techniques. Crown thinning primarily aims to reduce density within the crown, allowing more light and air circulation. Crown raising, on the other hand, involves removing lower branches to increase clearance beneath the tree. Implementing best practices for both techniques ensures the tree's long-term health and minimizes the risk of damage.


Effective crown thinning involves selectively removing smaller branches throughout the crown, typically targeting those that are crossing, rubbing, or growing inwards. The goal isn't to drastically alter the tree's shape but rather to enhance its structure and reduce the sail effect, making it less susceptible to wind damage. It's crucial to avoid over-thinning, which can weaken the tree and make it vulnerable to sunscald. A good rule of thumb is to remove no more than 25% of the live crown in a single pruning session. Cuts should be made cleanly, just outside the branch collar, to promote proper healing and minimize the risk of decay.


Crown raising focuses on removing lower branches to achieve a desired vertical clearance. This is often necessary for practical reasons, such as providing clearance for vehicles or pedestrians, improving visibility, or enhancing views. When raising the crown, it's important to maintain a balanced and natural appearance. Removing too many lower branches can weaken the tree's structure and make it top-heavy. Similar to thinning, cuts should be made cleanly just outside the branch collar. The height to which the crown is raised should be carefully considered, taking into account the tree species, its age, and its overall health.


Best practices for both crown thinning and raising include using sharp, sterilized pruning tools, making proper cuts, and avoiding flush cuts that damage the trunk. It's also essential to understand the tree's growth habit and pruning requirements. For larger or more complex pruning jobs, it's always recommended to consult with a certified arborist. Their expertise can help ensure that the pruning is done correctly, promoting the tree's health and longevity. By following these techniques and best practices, you can maintain healthy, beautiful, and structurally sound trees for years to come.

Crown Raising: Methods and Considerations —

Crown raising and thinning are common tree pruning practices, each serving a distinct purpose. While thinning focuses on reducing density within the crown, raising involves removing lower branches to achieve a specific clearance beneath the canopy. Let's delve into the methods and considerations for crown raising.


Several methods are employed for crown raising, the choice often depending on the tree species, its age, and the desired outcome. Small, lower branches can be removed with hand pruners, making clean cuts at the branch collar. For larger branches, lopping shears or a pruning saw might be necessary. Reciprocating saws are sometimes used for very large limbs, but careful technique is crucial to avoid tearing the bark. Regardless of the tool used, the fundamental principle remains consistent: make clean cuts that minimize damage and promote rapid healing.


Several considerations should guide the crown raising process. Firstly, avoid removing excessive live branches in a single pruning session, as this can stress the tree and make it susceptible to disease or decline. A general rule of thumb is to remove no more than 25% of the live crown in any given year. Secondly, the final height of the raised crown should be carefully considered. Raising the crown too high can weaken the tree and make it less stable, especially in windy conditions. A balanced crown is crucial for overall tree health and longevity. Thirdly, the branch collar, a slightly swollen area at the base of the branch, should be preserved during pruning. This collar contains specialized cells that facilitate wound closure, preventing decay. Cutting into the branch collar hinders this natural healing process and invites disease. Finally, the timing of crown raising can influence the tree's response. While some pruning can be done throughout the year, major crown raising is often best performed during the dormant season when the tree is not actively growing.


In conclusion, crown raising can be a beneficial practice when performed correctly, providing clearance for pedestrians, vehicles, or buildings while maintaining the tree's health and aesthetic appeal. By carefully considering the methods employed, the amount of live crown removed, the final crown height, the preservation of the branch collar, and the timing of the pruning, arborists can ensure the long-term health and structural integrity of the tree.

Citations and other links

Equipment and Safety Precautions for Crown Thinning and Raising

Crown thinning and raising are common tree pruning practices that improve light penetration and increase clearance beneath the canopy. However, they require specific equipment and adherence to strict safety precautions to prevent accidents and ensure effective results. Let's delve into the essentials.


For equipment, you'll need a combination of tools depending on the size and height of the tree. Hand saws, pruning shears, and loppers are sufficient for smaller branches. Pole saws and pruners extend your reach for higher limbs, while chainsaws are necessary for larger branches, especially during crown thinning. Remember, chainsaw use requires specific training and safety gear. Ropes, harnesses, and climbing spikes are crucial for accessing the crown of taller trees, enabling safe and controlled movement. A helmet, eye protection, gloves, and sturdy boots are non-negotiable for all pruning activities. First aid kit should always be readily available.


Safety is paramount when working at height and with sharp tools. Before starting, assess the tree for hazards like dead or weak branches, power lines, or unstable ground. Clear the work area below the tree to prevent injuries from falling debris. If using a chainsaw, ensure the chain is sharp and properly tensioned, and wear appropriate chainsaw chaps. When climbing, use a secure harness and rope system, and always have a second point of contact with the tree. Never overreach or climb beyond your skill level. Be mindful of fatigue, as it can lead to mistakes and accidents. Proper pruning cuts are also essential for tree health and should be made just outside the branch collar. Avoid flush cuts or tearing the bark, as these can create entry points for disease and pests.


Finally, consider the weather conditions. Avoid pruning during high winds, heavy rain, or lightning storms. Wet wood is heavier and more difficult to handle, increasing the risk of accidents. Proper planning, appropriate equipment, and a focus on safety will ensure successful crown thinning and raising while minimizing risks to both the tree and the arborist.

Equipment and Safety Precautions for Crown Thinning and Raising

Case Studies and Examples of Effective Crown Thinning and Raising

Crown thinning and raising are common tree pruning practices aimed at improving a tree's structure, health, and aesthetics. While both involve removing branches, they target different areas and achieve distinct outcomes. Thinning focuses on reducing density within the crown, while raising removes lower branches to increase clearance beneath the tree. Understanding the benefits and seeing real-world examples helps illustrate their effectiveness.


Crown thinning is like giving a tree a haircut that lets in more light and air. By selectively removing smaller branches throughout the crown, typically up to a quarter of the live branches, you improve light penetration and air circulation. This can reduce the risk of fungal diseases, lessen wind resistance (making the tree less susceptible to storm damage), and encourage stronger, healthier growth. For example, imagine a large oak tree overshadowing a garden. Thinning its dense canopy would allow more sunlight to reach the plants below, promoting their growth while also maintaining the oak's majestic form. Another example is thinning the crown of a fruit tree, which can improve fruit size and quality by increasing sunlight exposure and airflow, leading to better ripening and reduced disease.


Crown raising, on the other hand, is like giving a tree longer legs. By removing the lower branches, you increase the vertical clearance beneath the crown. This is often done along streets and sidewalks to improve visibility for drivers and pedestrians, or in private gardens to allow more space for underplanting or activities. A practical example is raising the crown of trees lining a driveway to allow for easier access by larger vehicles. Another common scenario is raising the crown of trees near power lines to prevent interference and reduce the risk of outages. In a park setting, raising the crown of trees can create inviting pathways and open spaces for recreation while preserving the trees' overall beauty.


Finding case studies that specifically detail the long-term effects of crown thinning and raising can be challenging, as detailed record-keeping of such practices isn't always readily available. However, arboricultural literature and experienced arborists can offer numerous examples and anecdotal evidence demonstrating their benefits. Visiting well-maintained parks, arboretums, or even observing street trees in your neighborhood can provide visual examples of how these techniques contribute to healthier, more aesthetically pleasing, and safer urban and natural environments. Ultimately, the effectiveness of crown thinning and raising depends on the skill of the arborist and the specific needs of the tree and its surrounding environment.

This article is about the pruning of plants in general. For the pruning of fruit bearing trees, see Fruit tree pruning. For other uses, see Pruning (disambiguation).
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Two workers pruning street trees in London during World War I

Pruning is a horticultural, arboricultural, and silvicultural practice involving the selective removal of certain parts of a plant, such as branches, buds, or roots.

The practice entails the targeted removal of diseased, damaged, dead, non-productive, structurally unsound, or otherwise unwanted plant material from crop and landscape plants. In general, the smaller the branch that is cut, the easier it is for a woody plant to compartmentalize the wound and thus limit the potential for pathogen intrusion and decay. It is therefore preferable to make any necessary formative structural pruning cuts to young plants, rather than removing large, poorly placed branches from mature plants.

Woody plants may undergo a process referred to as "self-pruning", where they will drop twigs or branches which are no longer producing more energy than they require. It is theorized that this process can also occur in response to lack of water, in order to reduce the surface area where water can be lost.[1] This natural shedding of branches is called cladoptosis.

Specialized pruning practices may be applied to certain plants, such as roses, fruit trees, and grapevines. Different pruning techniques may be used on herbaceous plants than those used on perennial woody plants.

Reasons to prune plants include deadwood removal, shaping (by controlling or redirecting growth), improving or sustaining health, reducing risk from falling branches, preparing nursery specimens for transplanting, and both harvesting and increasing the yield or quality of flowers and fruits.

Pruning terms

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Branch wood, trunk wood, branch collar, branch bark ridge clearly identified on a tree.
 

Branch wood

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Branch wood is an individual stem that grows off of another stem.

Trunk wood

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Trunk wood is the main stem of a tree which individual stems grow out of.

Branch collar

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This refers to the area below the union of where branch wood attaches with the trunk/stem wood. This can often appear raised.

Branch bark ridge

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This refers to the junction between branch wood and trunk/stem wood. It usually looks raised. [2]

Types of Pruning

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An arborist pruning a tree near the Statue of Liberty

Pruning in an urban setting is crucial due to the tree being in drastically different conditions than where it naturally grows.[3]

Arborists, orchardists, and gardeners use various garden tools and tree cutting tools designed for the purpose, such as secateurs, loppers, handsaws, or chainsaws.[4] Additionally in forestry, pole pruners (averruncators in British English) and pole saws are commonly used, and these are often attached to poles that reach up to 5–6 m (16–20 ft). This is a more efficient and safer way of pruning than with ladders. These bush saws on polls have also been motorized as chainsaws which is even more efficient. Older technology used Billhooks, Kaiser blades, and pruning knives. Although still used in some coppicing, they are not used so much in commercial forestry due to the difficulty of cutting flush with the stem. Flush cuts happen when a pruner cuts into the cambium layer of the main trunk, which can happen when a pruner is not precise with pruning cuts, and removes a portion of the branch collar, which can put the tree at risk of entry cords from forest pathogens.

Although there are several different types of pruning, they can be simplified into two categories. One of which is cutting the branch back to a specific and intermediate point, called a "reduction cut", and the other of which is completely removing a branch back to the union where the branch connects which the main trunk, called "removal cut".[5]

Dense growth results after shearing

A "reduction cut" is when one removes a portion of a growing stem down to a set of desirable buds or side-branching stems. This is commonly performed in well trained plants for a variety of reasons, for example to stimulate growth of flowers, fruit or branches, as a preventive measure to wind and snow damage on long stems and branches, and finally to encourage growth of the stems in a desirable direction.

  • Thinning: A more drastic form of pruning, a thinning out cut, is the removal of an entire shoot, limb, or branch at its point of origin.[5] This is usually employed to revitalize a plant by removing over-mature, weak, problematic, and excessive growths. When performed correctly, thinning encourages the formation of new growth that will more readily bear fruit and flowers. This is a common technique in pruning roses and for amplifying and "opening-up" the branching of neglected trees, or for renewing shrubs with multiple branches.
  • Topping: Topping is a very severe form of pruning which involves removing all branches and growths down to a few large branches or to the trunk of the tree. When performed correctly it is used on very young trees, and can be used to begin training younger trees for pollarding or for trellising to form an espalier.
  • Raising removes the lower branches from a tree in order to provide clearance for buildings, vehicles, pedestrians, and vistas. [6]
  • Reduction reduces the size of a tree, often for clearance for utility lines. Reducing the height or spread of a tree is best accomplished by pruning back the leaders and branch terminals to lateral branches that are large enough to assume the terminal roles (at least one-third the diameter of the cut stem). Compared to topping, reduction helps maintain the form and structural integrity of the tree.[7]

In orchards, fruit trees are often lopped to encourage regrowth and to maintain a smaller tree for ease of picking fruit. The pruning regime in orchards is more planned, and the productivity of each tree is an important factor.

Deadwooding

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Branches die off for a number of reasons including sunlight deficiency, pest and disease damage, and root structure damage. A dead branch will at some point decay back to the parent stem and fall off. This is normally a slow process but can be hastened by high winds or extreme temperatures. The main reason deadwooding is performed is safety. Situations that usually demand removal of deadwood include trees that overhang public roads, houses, public areas, power lines, telephone cables and gardens. Trees located in wooded areas are usually assessed as lower risk but assessments consider the number of visitors. Trees adjacent to footpaths and access roads are often considered for deadwood removal.[8]

Another reason for deadwooding is amenity value, i.e. a tree with a large amount of deadwood throughout the crown will look more aesthetically pleasing with the deadwood removed. The physical practice of deadwooding can be carried out most of the year though should be avoided when the tree is coming into leaf. The deadwooding process speeds up the tree's natural abscission process. It also reduces unwanted weight and wind resistance and can help overall balance.

Preventive structural pruning

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Preventative and structural pruning can be done to mitigate several issues young trees may have in the future. The structural pruning can reduce tree stress, increase the lifespan of trees, and promotes resistance to damage due to natural weather events. Attributes of trees with good structure include excurrent growth by having a single dominant leader, branch unions without included bark, and a balanced canopy. Structural pruning does this by developing or maintaining a dominant leader, identify the lowest branches in the canopy, prevent branches below the permanent canopy from growing too large, keeping all branches less than one half the trunk diameter, space main branches along one dominant trunk, and suppress growth on branches with included bark. [9]

Subordination pruning

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Subordination pruning is done on limbs that will exceed 50% percent of the stem diameter. A reduction cut may be performed while still allowing about 50% of the branch. This is done to help maintain form and deter the formation of co-dominant leaders. Temporary branches may be too large for a removal cut so subordination pruning should be done to slowly reduce a limb by 50% each year to allow the tree to properly heal from the cut. As a tree becomes larger the slower it grows. Reducing the larger limbs for eventual removal will allow for the tree to promote new growth rather than using energy in encouraging unwanted limbs to continue to grow. Removing a large branch increases the likelihood of the cut to not heal properly which also may attract insects, diseases and fungus. [9][10]

Crown thinning

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Crown thinning is the removal of live healthy branches which increases light penetration, air circulation and reduces wind resistance which reduces risks from damage and the possibility of pest infestation. [11]

Crown raising

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Crown raising involves the removal of the lower branches to a given height. The height is achieved by the removal of whole branches or removing the parts of branches which extend below the desired height. The branches are normally not lifted to more than one third of the tree's total height.

Crown lifting is done for access; these being pedestrian, vehicle or space for buildings and street furniture. Lifting the crown will allow traffic and pedestrians to pass underneath safely. This pruning technique is usually used in the urban environment as it is for public safety and aesthetics rather than tree form and timber value.

Crown lifting introduces light to the lower part of the trunk; this, in some species can encourage epicormic growth from dormant buds. To reduce this sometimes smaller branches are left on the lower part of the trunk. Excessive removal of the lower branches can displace the canopy weight, this will make the tree top heavy, therefore adding stress to the tree. When a branch is removed from the trunk, it creates a large wound. This wound is susceptible to disease and decay, and could lead to reduced trunk stability. Therefore, much time and consideration must be taken when choosing the height the crown is to be lifted to.

This would be an inappropriate operation if the tree species’ form was of a shrubby nature. This would therefore remove most of the foliage and would also largely unbalance the tree. This procedure should not be carried out if the tree is in decline, poor health or dead, dying or dangerous (DDD) as the operation will remove some of the photosynthetic area the tree uses. This will increase the decline rate of the tree and could lead to death.

If the tree is of great importance to an area or town, (i.e. veteran or ancient) then an alternative solution to crown lifting would be to move the target or object so it is not in range. For example, diverting a footpath around a tree's drip line so the crown lift is not needed. Another solution would be to prop up or cable-brace the low hanging branch. This is a non-invasive solution which in some situations may be more economical and environmentally friendly. [12]

Vista pruning

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Selectively pruning a window of view in a tree.

Crown reduction

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Reducing the height and or spread of a tree by selectively cutting back to smaller branches and in fruit trees for increasing of light interception and enhancing fruit quality.

Pollarding

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Main article: Pollarding

A regular form of pruning where certain deciduous species are pruned back to pollard heads every year in the dormant period. This practice is usually commenced on juvenile trees so they can adapt to the harshness of the practice. This practice can be used for tree shaping but is also used in specific species which young branches can be sold for floral arrangements.

Deadheading

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Deadheading is the act of removing spent flowers or flowerheads for aesthetics, to prolong bloom for up to several weeks or promote rebloom, or to prevent seeding.

Time period

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Pruning of trees in Chandigarh

In general, pruning deadwood and small branches can be done at any time of year. Depending on the species, many temperate plants can be pruned either during dormancy in winter, or, for species where winter frost can harm a recently pruned plant, after flowering is completed. In the temperate areas of the northern hemisphere autumn pruning should be avoided, as the spores of disease and decay fungi are abundant at this time of year.

Some woody plants tend to bleed profusely from cuts, such as mesquite and maple. Some callus over slowly, such as magnolia. In this case, they are better pruned during active growth when they can more readily heal. Woody plants that flower early in the season, on spurs that form on wood that has matured the year before, such as apples, should be pruned right after flowering as later pruning will sacrifice flowers the following season. Forsythia, azaleas and lilacs all fall into this category.

See also

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References

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  1. ^ BCMA, Jeremiah_Sandler (2021-02-01). "On Removing Deadwood, Part 1". Tree Care Industry Magazine. Retrieved 2024-05-30.
  2. ^ McKenzie, Rita; Holt, Harvey. "Trees Need a Proper Start – Prune Them Right" (PDF). Urban Forestry Specialists, Forestry and Natural Resources. Purdue University.
  3. ^ Fraedrich, Bruce. “Structural Pruning of Young Trees.” Bartlett Tree Research Laboratories Technical Report.
  4. ^ Encyclopedia of gardening (3rd U.S., rev. and updated ed.). London: DK Pub. 2012. pp. 554–556. ISBN 9780756698287.
  5. ^ a b "Tree Fruit Production Guide". tfpg.cas.psu.edu. Retrieved 20 December 2017.
  6. ^ "Raising - Pruning - Landscape plants - Edward F. Gilman - UF/IFAS". hort.ifas.ufl.edu. Retrieved 2024-05-28.
  7. ^ "Reducing - Pruning - Landscape plants - Edward F. Gilman - UF/IFAS". hort.ifas.ufl.edu. Retrieved 2024-05-28.
  8. ^ "Removal of dead wood - Nelson's Tree Services". Archived from the original on 15 December 2017. Retrieved 20 December 2017.
  9. ^ a b Gilman, Edward F.; Bisson, Amanda (2008-01-24). "Chapter 12 — Developing a Preventative Pruning Program: Young Trees". EDIS. 2008 (1). doi:10.32473/edis-ep315-2007. ISSN 2576-0009.
  10. ^ Gilman, Edward F. (2012). An illustrated guide to pruning (3rd ed.). Clifton Park, NY: Delmar. ISBN 978-1-111-30730-1.
  11. ^ "Crown Reduction - Nelson's Tree Services". Retrieved 20 December 2017.
  12. ^ Smiley, E, and Bruce Fraedrich. “Pruning Standard to Maintain Landscape Trees.” Bartlett Tree Research Laboratories Technical Report.

Bibliography

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  • Sunset Editors, (1995) Western Garden Book, Sunset Books Inc, ISBN 978-0-376-03851-7
  • James, N. D. G, The arboriculturalist's companion, second edition 1990, Blackwell Publishers Ltd, Great Britain.
  • Shigo, A, 1991, Modern arboriculture, third printing, Durham, New Hampshire, USA, Shirwin Dodge Printers.
  • Shigo, A, 1989, A New Tree Biology. Shigo & trees Associates.
  • J.M. Dunn, C.J. Atkinson, N.A. Hipps, 2002, Effects of two different canopy manipulations on leaf water use and photosynthesis as determined by gas exchange and stable isotope discrimination, East Malling, University of Cambridge.
  • Shigo. A. L, 1998, Modern Arboriculture, third printing (2003), USA, Sherwin Dodge Printers
  • British standards 3998:1989, Recommendations for Tree Work.
  • Lonsdale. D, 1999, Principles of tree hazard assessment and management, 6th impression 2008, forestry commission, Great Britain.
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Wikiversity has learning resources about Arboriculture/Pruning
 
 

 

See also: Tree care and Urban forestry
An arborist practicing tree care: using a chainsaw to fell a eucalyptus tree in a park at Kallista, Victoria.

Arboriculture (/ˈɑːrbərɪˌkʌltʃər, ɑːrˈbɔːr-/)[1] is the cultivation, management, and study of individual trees, shrubs, vines, and other perennial woody plants. The science of arboriculture studies how these plants grow and respond to cultural practices and to their environment. The practice of arboriculture includes cultural techniques such as selection, planting, training, fertilization, pest and pathogen control, pruning, shaping, and removal.

Overview

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A person who practices or studies arboriculture can be termed an arborist or an arboriculturist. A tree surgeon is more typically someone who is trained in the physical maintenance and manipulation of trees and therefore more a part of the arboriculture process rather than an arborist. Risk management, legal issues, and aesthetic considerations have come to play prominent roles in the practice of arboriculture. Businesses often need to hire arboriculturists to complete "tree hazard surveys" and generally manage the trees on-site to fulfill occupational safety and health obligations.[citation needed]

Arboriculture is primarily focused on individual woody plants and trees maintained for permanent landscape and amenity purposes, usually in gardens, parks or other populated settings, by arborists, for the enjoyment, protection, and benefit of people.[citation needed]

Arboricultural matters are also considered to be within the practice of urban forestry yet the clear and separate divisions are not distinct or discreet.[citation needed]

Tree Benefits

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Main article: Urban forestry § Benefits

Tree benefits are the economic, ecological, social and aesthetic use, function purpose, or services of a tree (or group of trees), in its situational context in the landscape.

Environmental Benefits

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  • Erosion control and soil retention
  • Improved water infiltration and percolation
  • Protection from exposure: windbreak, shade, impact from hail/rainfall
  • Air humidification
  • Modulates environmental conditions in a given microclimate: shields wind, humidifies, provides shade
  • Carbon sequestration and oxygen production

Ecological Benefits

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  • Attracting pollinators
  • Increased biodiversity
  • Food for decomposers, consumers, and pollinators
  • Soil health: organic matter accumulation from leaf litter and root exudates (symbiotic microbes)
  • Ecological habitat

Socioeconomic Benefits

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  • Increases employment: forestry, education, tourism
  • Run-off and flood control (e.g. bioswales, plantings on slopes)
  • Aesthetic beauty: parks, gatherings, social events, tourism, senses (fragrance, visual), focal point
  • Adds character and prestige to the landscape, creating a "natural" feel
  • Climate control (e.g shade): can reduce energy consumption of buildings
  • Privacy and protection: from noise, wind
  • Cultural benefits: eg. memorials for a loved one
  • Medical benefits: eg. Taxus chemotherapy
  • Materials: wood for building, paper pulp
  • Fodder for livestock
  • Property value: trees can increase by 10–20%[citation needed]
  • Increases the amount of time customers will spend in a mall, strip mall, shopping district[citation needed]

Tree Defects

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A tree defect is any feature, condition, or deformity of a tree that indicates weak structure or instability that could contribute to tree failure.

Common types of tree defects:

Codominant stems: two or more stems that grow upward from a single point of origin and compete with one another.

  • common with decurrent growth habits
  • occurs in excurrent trees only after the leader is killed and multiple leaders compete for dominance

Included bark: bark is incorporated in the joint between two limbs, creating a weak attachment

  • occurs in branch unions with a high attachment angle (i.e. v-shaped unions)
  • common in many columnar/fastigiate growing deciduous trees

Dead, diseased, or broken branches:

  • woundwood cannot grow over stubs or dead branches to seal off decay
  • symptoms/signs of disease: e.g. oozing through the bark, sunken areas in the bark, and bark with abnormal patterns or colours, stunted new growth, discolouration of the foliage

Cracks

  • longitudinal cracks result from interior decay, bark rips/tears, or torsion from wind load
  • transverse cracks result from buckled wood, often caused by unnatural loading on branches, such as lion's tailing.
  • Seams: bark edges meet at a crack or wound
  • Ribs: bulges, indicating interior cracks

Cavity and hollows: sunken or open areas wherein a tree has suffered injury followed by decay. Further indications include: fungal fruiting structures, insect or animal nests.

Lean: a lean of more than 40% from vertical presents a risk of tree failure

Taper: change in diameter over the length of trunks branches and roots

Epicormic branches (water sprouts in canopy or suckers from root system): often grow in response to major damage or excessive pruning

Roots:

  • girdling roots compress the trunk, leading to poor trunk taper, and restrict vascular flow
  • kinked roots provide poor structural support; the kink is a site of potential root failure
  • circling roots occurs when roots encounter obstructions/limitations such as a small tree well or being grown too long in a nursery pot; these cannot provide adequate structural support and are limited in accessing nutrients and water
  • healthy soil texture and depth, drainage, water availability, makes for healthy roots

Tree Installation

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See also: Tree planting

Proper tree installation ensures the long-term viability of the tree and reduces the risk of tree failure.

Quality nursery stock must be used. There must be no visible damage or sign of disease. Ideally the tree should have good crown structure. A healthy root ball should not have circling roots and new fibrous roots should be present at the soil perimeter. Girdling or circling roots should be pruned out. Excess soil above the root flare should be removed immediately, since it presents a risk of disease ingress into the trunk.

Appropriate time of year to plant: generally fall or early spring in temperate regions of the northern hemisphere.

Planting hole: the planting hole should be 3 times the width of the root ball. The hole should be dug deep enough that when the root ball is placed on the substrate, the root flare is 3–5cm above the surrounding soil grade. If soil is left against the trunk, it may lead to bark, cambium and wood decay. Angular sides to the planting hole will encourage roots to grow radially from the trunk, rather than circling the planting hole. In urban settings, soil preparation may include the use of:

  • Silva cells: suspended pavement over modular cells containing soil for root development
  • Structural soils: growing medium composed of 80% crushed rock and 20% loam, which supports surface load without it leading to soil compaction

Tree wells: a zone of mulch can be installed around the tree trunk to: limit root zone competition (from turf or weeds), reduce soil compaction, improve soil structure, conserve moisture, and keep lawn equipment at a distance. No more than 5–10cm of mulch should be used to avoid suffocating the roots. Mulch must be kept approximately 20cm from the trunk to avoid burying the root flare. With city trees additional tree well preparation includes:

Tree grates/grill and frames: limit compaction on root zone and mechanical damage to roots and trunk

Root barriers: forces roots to grow down under surface asphalt/concrete/pavers to limit infrastructure damage from roots

Staking: newly planted, immature trees should be staked for one growing season to allow for the root system to establish. Staking for longer than one season should only be considered in situations where the root system has failed to establish sufficient structural support. Guy wires can be used for larger, newly planted trees. Care must be used to avoid stem girdling from the support system ties.

Irrigation: irrigation infrastructure may be installed to ensure a regular water supply throughout the lifetime of the tree. Wicking beds are an underground reservoir from which water is wicked into soil. Watering bags may be temporarily installed around tree stakes to provide water until the root system becomes established. Permeable paving allows for water infiltration in paved urban settings, such as parks and walkways.

UK

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Within the United Kingdom trees are considered as a material consideration within the town planning system and may be conserved as amenity landscape[2] features.

The role of the Arborist or Local Government Arboricultural Officer is likely to have a great effect on such matters. Identification of trees of high quality which may have extensive longevity is a key element in the preservation of trees.

Urban and rural trees may benefit from statutory protection under the Town and Country Planning[3] system. Such protection can result in the conservation and improvement of the urban forest as well as rural settlements.

Historically the profession divides into the operational and professional areas. These might be further subdivided into the private and public sectors. The profession is broadly considered as having one trade body known as the Arboricultural Association, although the Institute of Chartered Foresters offers a route for professional recognition and chartered arboriculturist status.

The qualifications associated with the industry range from vocational to Doctorate. Arboriculture is a comparatively young industry.

See also

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References

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  1. ^ "arboriculture". Dictionary.com Unabridged (Online). n.d.
  2. ^ "Amenity landscapes • Environment Guide". www.environmentguide.org.nz. Retrieved 2020-04-28.
  3. ^ "Town and Country Planning Association". Town and Country Planning Association. Retrieved 2020-04-28.
  • Harris, Richard W. (1983). Arboriculture: Care of Trees, Shrubs, and Vines in the Landscape. Englewood Cliffs, New Jersey: Prentice-Hall, Inc. pp. 2–3. ISBN 0-13-043935-5.
  • "arboriculture". Merriam-Webster's Collegiate Dictionary, Eleventh Edition. Merriam-Webster.
  • "arboriculture". Encyclopædia Britannica Online. 2007.
  • "arboriculture". The American Heritage Dictionary of the English Language, Fourth Edition Online. Houghton Mifflin Company. 2000.
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Wikisource has the text of the 1905 New International Encyclopedia article "Arboriculture".
 
 

 

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Frequently Asked Questions

Crown thinning removes a portion of smaller branches within the crown to reduce density and increase light penetration, while crown raising removes lower branches to increase clearance beneath the tree.
Thinning improves air circulation, reduces wind resistance, and can lessen the risk of limb failure. Raising provides clearance for vehicles, pedestrians, buildings, or sightlines.
Excessive thinning or raising can harm the tree. Generally, no more than 20-25% of the live crown should be removed at one time. Raising should leave sufficient foliage for the trees health.
While small branches can sometimes be pruned by homeowners, crown thinning and raising, especially on larger trees, often require specialized equipment and expertise. Improper techniques can damage the tree and create hazards, so hiring a certified arborist is usually recommended.