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Protection of Trees
By-law (No. 9958) (PDF)
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Root Protection and Pruning
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Root Protection and Pruning
General Info: Heavy equipment or repeated foot traffic can seriously
damage the roots of a tree to the point where they will not survive.
Roots need pore space within the soil for growth and this critical pore
space is destroyed when the soil is compacted by heavy weights.
All trees to be retained on your site require protection during any construction
or development. All trees on adjacent properties or boulevard trees
which are in danger of being damaged must be protected as well. Click
here for information on tree barriers.
Root Pruning
Root Pruning is the practice of removing a portion of a tree’s root system.
Adding soil and reseeding is recommended as a first step to prevent the
removal of key structural roots. However, root pruning sometimes
becomes necessary in order to accommodate landscape features such as walks,
retaining walls, drains, or utilities.
The circumstances necessitating root pruning vary, but the objective
of the tree root pruning is always to ensure the health, stability, and
longevity of the tree.
Note: The new Protection of Trees By-law [pdf] requires that root pruning be done by an Arborist.
Root Pruning Guidelines
The following general root pruning guidelines are provided for your knowledge:
- A tree should be root pruned only if the problem can be solved by
removing less than 33 percent of the tree’s roots, with no more than
25 percent from one side.
- For trees 30 cm in diameter and less, roots should not be removed
within 1.2 m of the outer edge of the tree base. Trees with diameters
over 30 cm should be allowed an additional 30 cm for every extra 7.5
cm of trunk diameter measured at a point 1 m above ground. For
example, a tree with a 37.5 cm diameter trunk measured 1 m above the
ground would require a minimum 1.55 m allowance around it. The
following table provides a guideline for root pruning different tree
sizes.
|
TREE DIAMETER |
DISTANCE
FROM TRUNK |
| (measured 1 m above ground) |
Minimum |
Preferred |
| 15 cm |
1.2 m |
1.5 m |
| 22.5 cm |
1.2 m |
1.5 m |
| 30 cm |
1.2 m |
1.8 m |
| 37.5 cm |
1.5 m |
2.1 m |
| 45 cm |
1.8 m |
2.4 m |
| 52.5 cm |
2.1 m |
2.7 m |
Cut roots cleanly after excavation with clean, sharp
tools, to promote callus formation and wound closure. Wounds
may be dressed with a tree rooting hormone compound that is available
at garden centres.
- Backfill the excavation as soon as possible and water the soil around
the roots to avoid leaving air pockets. If backfilling won't happen
for several days, leave the roots exposed until just before backfilling.
- Mix soil improvements (e.g., peat moss) with fill soil to promote new
root growth, especially if the existing soil is of poor quality.
The soil quality can be easily determined by using a basic soil testing
kit which is readily available at most nursery supply stores.
Do not add fertilizers until improved tree growth is noticed,
generally after 6 to 8 weeks during a growing season. Soil testing
will better determine soil deficiencies and additional amendment requirements
if necessary.
- Surface roots which interfere with other elements in the landscape should only be removed by an Arborist. Each tree has a different root system and requires individual analysis and treatment.
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