Arborist Report: Assessment of Condition and Risk Potential - 29 Tovey Crescent

Re: 29 Tovey Crescent

Assignment:

Assess the condition and risk potential of a mature pine tree that is located on the left hand side of the driveway (facing house) at 29 Tovey Place. (The property owner is concerned that it looks poorly and leans towards the neighbour’s property.) Assess the condition of a mature Douglas fir tree located on the edge of the driveway opposite the arbutus. Assess the condition of a double-stemmed Douglas fir located along the south boundary of the property.

Methodology:

The trees were visually assessed by Jeremy Gye on November 27, 2018. No boring, excavation or aerial inspection was attempted. A Level-2 (Basic) Tree Risk Assessment was completed of the mature pine.

Observations:

The pine is a Ponderosa pine that is approximately 80 cm in diameter at breast height and is approximately 16 - 18 metres tall. The tree’s trunk leans in a north-easterly direction toward the neighbour’s service drop and driveway. The lean of the tree is approximately 25 degrees off vertical (see Photo A). The upper crown of the tree has begun to assume a more vertical orientation. A mature 80cm diameter Douglas fir is located directly across the driveway from the pine.

A visual inspection of the pine suggests that the tree was topped approximately 20 – 30 years ago and has since reformed a new leader. A “stub” of the original leader was left at the time of topping, a portion of which is still visible. The stub appears relatively small (15 – 20cm) in relation to the diameter of the trunk below the new leader (40 – 45cm) (see Photo B). The leader appears well attached to the trunk in a “dog leg” fashion typical of a lateral branch that has turned up to form a new leader. The diameter of the re-generated leader blends smoothly into the trunk.

The reformed leader accounts for approximately 90% of the live crown of the pine. One can easily see through the pine’s canopy, which appears less opaque than is typical for an open grown specimen of this species (see Photo D). Small cracks are present in the concrete driveway next to the tree (see Photo E).

The Douglas fir located on the edge of the driveway is approximately 80cm in diameter and 20m tall+/- (see Photo F). The tree has a live crown ratio of 50%. There are no visible defects, apart from the loss of a small top. The tree exhibits a stable distribution of first-order lateral roots and there is no visible indication that there is any instability at the base of the tree. The canopy of the tree appears to be struggling, exhibiting lower than normal leaf density for an open grown tree. The colour of the leaves is also not as dark as it would be in a healthy fir.

The double-stemmed fir growing along the south boundary appears in good health (see Photo G). The sub-dominant stem has developed a photo-tropic lean towards the house. The union of the two stems is narrow with some included bark.

Discussion:

Pine tree: The relatively small size of the original topping wound (see above) combined with the healthy stem girth and morphology around the attachment point of the current leader suggests that this point in the tree’s structure is sound (see Photo C) and unlikely to have extensive decay associated with it.

The concentration of the live crown within the upper portion of a soft-wood tree like a pine places the tree at a somewhat higher risk of crown failure than otherwise. If the root system of the tree is compromised by the adjacent driveway, the live crown ratio may also place the tree at a higher risk of whole tree failure at the root plate. If the crown or the tree-as-a-whole were to fail, potential targets include the neighbour’s service drop, car(s) parked in the driveway or the corner of the deck attached to the house.

From a risk perspective, the likelihood of a failure is rated as possible; likelihood of the tree impacting a high-value target is rated as high; the likelihood of a failure resulting in an impact is rated as somewhat likely; the consequence of an impact is rated as significant; and the overall risk of the tree in its present condition to the neighbour is currently rated as moderate.

The somewhat sparse condition of the canopy may be an indication of diminished vitality, possibly due to reduced annual precipitation and a significant amount of impervious driveway surface overtop of the root system of the tree.

The emerging cracks in the driveway may be associated with either root growth or root movement. It would be informative to watch the base of the tree during strong wind to see if there is any movement at the base of the stem, which would indicate an unstable root plate. In any event, the close proximity of the base of the tree to the driveway (Photo E) indicates that cracking and heaving of concrete will get worse in the short to medium term. The tree presents a more than normal risk of both a partial and a whole tree failure.

Fir tree by driveway: It’s unclear why the health of this tree is deteriorating. One speculation is that the change in condition is a delayed response to the installation of the driveway or of the lack of soil moisture and nutrient cycling within the portion of root habitat covered over by the concrete driveway.

Double-stemmed fir: The double-stemmed configuration of this tree is not ideal in the longer term. As the sub-dominant stem develops in size over time, the risk of a failure at the stem union will increase, it will inhibit the branch development on the north side of the dominant stem and it will begin to impose upon the open and sunny landscape of the front yard. The sub-dominant stem is still young and small enough to be removed before it begins adversely impacting the form and branching habit of the parent stem.

Recommendations:

Pine tree: The risk of failure and future driveway damage can best be managed through cutting the pine to ground level and replacing it with another tree in a more suitable location.

Fir tree by driveway: We recommend that this tree be monitored over time. If the health and condition of the tree continue to deteriorate, removal of the tree is recommended.

Double-stemmed fir: We recommend that the sub-dominant stem growing toward the house be removed.

Respectfully submitted,

Jeremy Gye – Senior Consultant Gye and Associates, Urban Forestry Consultants Ltd.

Consulting Arborist (Diploma, American Society of Consulting Arborists, 1997) ISA Certified Arborist (Certification No. PN-0144A) ISA Municipal Specialist (Certification No. PN-0144AM) ISA Tree Risk Assessment Qualified