Basic Arboricultural Terms

Here we define a little bit more on the basic Arboricultural terms used and hopefully explain what they mean.  Of course if you would like advice, please send us an email or give us a call.

What is Crown Lifting
Definition: raising the canopy of the tree.
 
Crown Lifting is the selective pruning/removal of lower branches to increase the distance between the ground level and the lower crown and is normally used to give a uniform height.  This process is normally carried out where there is a need to clear footpaths, roads, signs and also allows for increased light.  UK common practice clearance for vehicles is 5.2 metres (17ft) and for pedestrians 2.5 metres (8ft).  This type of pruning should ideally be completed before a tree reaches maturity to avoid creating large wounds and when done correctly does much less damage to a tree than reducing the canopy size.

What is Crown Reduction?
Definition:  Reduction of the height and/or spread of the tree through proper pruning practices.
 
Crown reduction is used to reduce the height and/or spread of the crown of a tree by the removal of the ends of branches whilst maintaining the tree’s natural shape as far as practicable.
 
The objective is to make cuts so that the foliage is left intact on the outer edge of the new, smaller canopy ideally, pruning cuts should not be evident when you stand back from the tree after pruning. Topping, shearing, tipping, and rounding over are not appropriate techniques for reducing the size of the tree because they compromise the tree’s structure and can cause decay.  We would recommend when removing more than 30% of the foliage, that you consider dividing the job into 2 sessions, around 12 months apart to minimize sprouting and starch removal from the tree.
 
It requires substantial talent to perform this operation; of course this is a temporary measure because the tree will quickly revert to its natural size. Crown reduction is quoted as percentage of leaf space not volume or height.  In many instances, canopies cannot be properly reduced in size to the extent desired and certain species such as Beech do not lend themselves to crown reduction, without special techniques such as pollarding.
 
It is very difficult to use crown reduction to permanently maintain a tree at a smaller size without causing the tree to decline. Consider pollarding to reduce and maintain the height if the tree is young. However tree removal and replacement with a smaller maturing plant may be the choice that minimizes the input of resources.
 
When a customer wishes to reduce the height, crown reducing is much preferred to topping. Crown reduction should not be used to reduce the chances of the tree blowing over in a storm. Thinning is the preferred method to minimize storm damage of an otherwise structurally sound tree. Crown reduction can be considered when the root system of a large maturing tree has substantial decay making it potentially hazardous or on a tree with a high rating. We would suggest considering pollarding or planting a smaller maturing tree for the site.

What is Crown Thinning?
Definition:  Removes branches from the crown without reducing the extent of the crown.
 
Thinning is used to reduce limb weight on mature trees in order to compensate for structural defects such as cracks, hollows, and cavities. Thinning is also used on a young tree to slow growth rate on a vigorous branch.  On occasions the severity of some diseases and pest infestations can be reduced by crown thinning because more light and air can move through a thinned canopy, this keeps the foliage drier, which discourages diseases. Thinning can also emphasize the beauty of the trunk and main branches and increase light penetration to the ground, which can enhance plant growth under the tree to a limited degree.
 
Proper thinning will not change the overall size of the tree, it will remain the same height and width as it was before thinning.  Proper thinning is done on relatively small branches in the leafy area of the canopy towards the ends of the main branches, whereas structural pruning is done on larger branches lower on the tree towards the trunk or anywhere it is needed.

What is Pollarding?
Definition: maintaining/reducing a tree to a specified height.
 
A frequently misunderstood term, and used in two different contexts. Traditionally and still commonly used this term describes the removal of all branches from the trunk.  Mature trees that have not been pollarded before are generally not suitable candidates for this type of pollarding due to the large wounds that such treatment produces which may jeopardise the long term future of the tree. A less frequently used definition can mean the regular (annual or biannual) pruning back of small branches to the same point resulting in the formation of a ‘pollard head’. Pollarded trees usually require regular treatment of re-growth.
 
Traditionally, trees have been maintained at 20-30ft tall. Pollarding can be used to keep a large, mature tree small.  It is also useful to control size if a tree has been planted too close to structures such as buildings, street lighting or electric wires.
 
Once begun it is essential that pollarding continues. Preferably, the pollarding process should begin when a tree is very young.
 
It should be noted that different species of trees respond to pollarding in different ways and pollarding may not be suitable.   Willow Trees have approximately 95% survival rate whereas Beech Trees rarely survive the procedure.

Tree Felling
Definition: The removal of a tree/s to leave a stump.
 
It is sometimes necessary to remove a tree if it is dead, dying or dangerous and this can be removed as one piece, depending of the site location/layout or taken down in sections.
 
At Castle Tree Care we are the leading Lincolnshire tree services in large tree removal and have many years experience in removing dangerous trees.  When removing dangerous trees we will often use a crane to ensure the safe removal of large stems and the final stem and ensuring site safety.