Hello gardeners!

Trees are among the most resilient and long-lived organisms on the planet, yet they are not invincible. Human actions often play a significant role in determining whether a tree can withstand the environmental stressors of climate change.

Poor Planting Practices: Setting Trees Up for Failure

A tree’s success begins at planting. Planting a tree too deep, covering the root flare with soil or mulch, can lead to issues like root rot, girdling roots, and poor oxygen exchange, ultimately weakening the tree. Conversely, planting too shallowly exposes roots to drying and a weak root infrastructure.

Soil compaction restricts root growth and water penetration, depriving the tree of the essential nutrients it needs to establish itself. Consider trees planted too close to driveways and buildings, not to mention street trees planted in small squares of compacted soil.

Selecting the wrong tree for the site is a common error. A tree poorly matched to its environment is more likely to experience stress, making it susceptible to disease and environmental pressures.

Poor Pruning Techniques: Weakening Tree Structure

Pruning when done incorrectly can cause irreversible damage. Topping, where large sections of a tree’s crown are cut back indiscriminately, is one of the most harmful practices. If the tree does regrow, these new shoots are poorly attached and prone to breaking in storms.

Similarly, improper cuts—such as leaving large stubs or making flush cuts too close to the trunk—can prevent the tree from healing properly. Open wounds create entry points for disease and pests, further weakening the tree.

I believe incorrect pruning is one of the primary causes of weak trees. When I see damage from heavy wind or snow, it is often on a tree that has been poorly pruned in the past.

*Photo taken by R. Pak at UBC Botanical Garden January 29, 2025.*

The Role of Watering: Too Much or Too Little

Water is essential for tree health, but both overwatering and underwatering can cause problems. Newly planted trees require consistent watering to establish deep roots, yet many trees suffer because they receive either too much or too little moisture.

Overwatering can suffocate roots by depriving them of oxygen, leading to root rot. On the other hand, prolonged drought conditions weaken trees, making them more susceptible to disease and structural failure. Once weakened, a tree is far more likely to be impacted by extreme weather events, such as heatwaves or storms.

Drought can permanently alter the physiological processes of a tree by contributing to a restriction of the xylem flow. The taller the tree, the more susceptible it is too drought because its natural water processes can be impacted before the soil is completely dry. By the time the soil dries out completely, the damage is already done.

*Photo taken by R.Pak in a Surrey, BC neighbourhood.*

Environmental Stressors: Disease, Lightning, Wind, and Fire

Even with the best care, trees still face natural threats. Disease can spread through wounds, poor soil conditions, or pest infestations. Lightning strikes can kill a tree instantly or weaken it over time. Strong winds uproot trees with shallow root systems, while fire can destroy entire forests.

Trees that are properly planted, pruned, and watered, develop strong root systems and resilient structures, making them better equipped to survive climate extremes.

Trees provide so many important benefits in the garden, for humans, birds and wildlife, and for the most part, are generally very low maintenance.