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Maureen Sexsmith-West

ISA Certified Arborist, PR4600A

Cracks are one of the most important indicators of structural weakness in a tree.

Frost Crack

FROST CRACKS: Our region is both blessed and cursed with Chinook winds. For plants and trees the increase in sudden temperature signals the coming of spring. Most significantly is the movement of sap. Prolonged periods of mild temperatures followed by a sudden drop can cause the either the trunk to split or branches to crack because fluids freeze and expand. Swelling leaf buds are also susceptible to frost damage.

Frost cracks are common in our region. They are generally found on the west and/or south side of trees but can originate at a point where previous damage was done (mower damage, poor pruning cuts). They appear to close in mild weather and open when cold. Smaller cracks in the cambium (or bark) can provide access to the inner wood of the tree where disease and fungal matter can cause extensive damage. Repeated injury can occur from year to year, never allowing the tree to fully repair the split.

Repeated annual damage of frost crack – this crack exceeds 50% of the tree’s diameter. It is hidden by new wound wood attempting to protect the trunk.

STRESS CRACKSresult from heavy, wet snow loads and over-thinned (lion tailed) branches under wind loads. The branches will either break free or will bend but will not rebound to their original position. Stress cracks are most often found on top of the branch and are not easily detected from the ground. Some branches may remain but pruning to prevent further damage is recommended. The void allows increased sunlight into the canopy and branch will begin to grow or old ones with fill in the void (phototropism).

Stress Crack

Not every crack is bad – it is the position on the tree and the depth of the crack which make it a potential hazard. Cracks which appear at or near the crotch of limbs compromise the holding strength of the wood. Your Certified Arborist can provide you with an expert opinion on the safety or hazard potential and advise you on the best course of action.

In some cases your tree can be stabilized using specialized bolts and cables. This procedure can be costly and should be weighed against the overall age, value, function and location of the tree. Proper placement and the number of cables used is determined by the characteristics of the particular tree. It should allow for movement and be installed a specific distance above the defect to be effective.

Systems will not prevent your tree from failure but it can save your roof or car from being crushed and provide a level of public safety by preventing it from falling. It will extend the enjoyment of your tree for a few years while a replacement can be planted and begin to grow. All stabilization programs should include removal of the ‘end weight’ (not the inside branches which give the branch strength) – this is called crown reduction. To maintain aesthetics, balance and natural form the tree should be pruned to suitable branches – no topping/stub cuts.

Illustration reproduced from Sherril Arborists Supply Catalogue

Annual inspections are recommended to ensure the system is still sound and pruning scheduled about every three years to manage end weight should also be part of your long term aftercare program. Depending on tree condition, further options such as removal of any potentially hazardous branches or complete removal and replacement may be presented.

CHECK UP: Take time to observe your tree from ALL SIDES and in ALL SEASONS. Become familiar with how your tree looks from year to year and you will soon be able to notice irregularities. Early detection can save your tree. Keep a photo journal and monitor any changes. Preventative care is always your best option. Contact us for a professional risk assessment.


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