Branch unions
Risks
Poor unions may be a significant weak point in the structure of the tree .
Loading unions ‘ outwards ’ may cause structural failure .
Look for acute unions and / or included bark , as discussed elsewhere in this manual .
Additionally , look for any evidence of decay or reduced structural integrity .
The image above shows an extremely acute bifurcation - this may be a weak and compromised union . Understanding tree species is important . Some species with these bark inclusions rarely fail , while others are more likely to fail .
Control measures
Investigate weakness of union if possible . Avoid loading if possible .
Load test if possible .
Brace or guy if necessary . Load union in compression .
Cracks or splits
Risks
If cracks are found on both sides of the stem , the load-bearing capacity may be significantly reduced ( by more than 50 %).
Cracks are narrow breaks or fissures in stems or branches . These occur for many reasons , and in some circumstances , trees may tolerate such cracks for many years , or even cover the crack completely with new growth .
Look for evidence of woundwood ( rolled , smooth new wood around the crack ) to gauge how long the crack has been present . Newer cracks may be of more concern as the tree has :
Structural failure may occur at low and unpredictable loads .
Control measures
Avoid loading if possible .
Load test if possible . Brace , strap , cinch or guy if necessary .
• had less time to put on adaptive growth to compensate for the weakness .
• been through fewer high wind events since the crack occurred .
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