How to Check a Tree's Health
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Thinning Leaves
Stand beneath the tree—can you see the sky through the branches? A healthy tree crown should be lush and full, providing shade and absorbing sunlight. If the canopy looks sparse, it could indicate stress from pests (such as the oak processionary moth) or diseases like ash dieback, which disrupts water flow and causes leaf loss.
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Discolored Leaves
The color of a tree's leaves can tell you a lot. Healthy green leaves mean efficient photosynthesis, but yellow, brown, or prematurely falling leaves are warning signs. Uneven color or size might indicate nutrient deficiency or poor root function, often due to waterlogging, soil compaction, or drought.
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Dieback and Deadwood
Check the branch tips—are there many small dead twigs or dying branches? This could mean the tree is stressed. Healthy trees grow new branches each year, so if parts of the crown are dying, it’s a strong indicator that something’s wrong.
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Dead or Flaking Bark
The bark is a tree’s protective layer. If you notice sticky, sap-like fluid leaking from the trunk, it could mean trouble within the tree’s cambium layer. This might be caused by fungal or bacterial infections or even pest damage from insects like the great spruce bark beetle.
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The Trunk
The trunk is the backbone of the tree, supporting the crown and transporting nutrients. Look for cracks, bulges, or wounds in the bark, as these can weaken the tree structurally and allow pathogens to enter.
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Roots
The roots anchor the tree and provide it with water and nutrients. Exposed or damaged roots, or any recent digging around them, can disrupt this system and weaken the tree. Check for visible root damage, especially after any nearby soil disturbance.
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Fungi
Certain fungi, like honey fungus, can be lethal to trees by killing their roots. Look for signs such as white fungal mats, black “bootlace” rhizomorphs under the bark, or honey-colored mushrooms around the base in late summer. Bracket fungi, like Ganoderma, can also indicate internal decay.
