When we were considering what questions were asked more than any others, there was one that stood out head and shoulders above all the rest: “What is wrong with my tree?” Of course, there is no way we can answer this question for each and every person, but we can give you a strategy for observing your trees which will help you determine if they have a problem and what you may be able to do to correct it. The life of a tree in danger can often be saved if the decline spiral is reversed.
If you suspect the health of your tree is in decline, we advise following a course of observation that examines the traits that indicate whether the tree is getting all the resources it needs and whether it is being threatened by external forces.
Consider The Tree’s History
The first step is to review the history of the tree. What type of tree is it? How old is it? Is your climate zone compatible with the tree’s needs? How long has it been on the site? What are the elements of the hardscape such as sidewalks, curbs, decks, pools, and sprinkler systems, that are close enough to the tree to affect its health?
This last question is often the most crucial because three-quarters of urban tree deaths can be attributed to root damage. It is important to note if any digging has been done inside the drip line.
The drip line is a circle around the tree with the trunk at its center and its circumference the outermost tips of the tree’s leaves. Even if the digging was done over five years in the past, it may be a significant factor in the health of the tree.
Some trees, such as the cedar, go into decline almost immediately if they suffer root damage, while others, like the oak, may take five years or more to show the effects of root damage, and people often fail to associate the decline in a tree’s health with changes in its root system.
Most of a tree’s root system is within 24 to 30 inches of the soil surface, so the danger to a tree posed by digging within its drip zone cannot be overstated.
Inspect The Root And Crown
Once the tree’s history has been reviewed, and any changes in the hardscape noted, the tree can be examined for clues to its health, it is recommended to start at the root crown because so many of the threats to the tree’s health start there. Is the tree at “original grade”, meaning does the tree enter the soil at the same depth at which it was planted? Is the root crown flare above ground and in good condition? A common mistake made by well-meaning gardeners is to cover the root crown with soil or mulch. While we strongly recommend using mulch as a way to conserve soil moisture and keep it friable, it is not advisable to cover the root crown itself. This area needs to breathe, and when it is buried it is vulnerable to attack by insects, fungi, and microorganisms that thrive in moist dark conditions.
The condition of the soil is an important factor in determining the health of the tree. What is the soil’s ability to absorb water? If the area under the tree is kept clear by frequent raking and leaf-blowing or is subject to heavy foot or vehicle traffic, the soil often becomes compacted and may no longer allow water to penetrate the root zone.
A tree may be exposed to adequate amounts of water, but if the water runs off before the tree can access it, there is clearly a hazard to the long-term health of the tree.
As we stated above, we recommend a mulch of leaf, bark, and other organic materials spread three to four inches thick within the drip line, up to but not touching the root crown flare, as a way of suppressing weeds, maintaining good soil conditions, and enhancing water absorption by stabilizing soil temperature and moisture. Mulch also feeds beneficial soil organisms like earthworms that ventilate and fertilize the soil and protects roots that have emerged from the soil surface from damage by mowers, a common problem for lawn trees.
Examine The Soil & Roots
Lawnmower damage can often be observed while examining the soil and roots, and if discovered early enough, can usually be reversed.
Gardening tools can be a serious hazard to trees. As our examination moves from the soil up the trunk of the tree, we look for indications of weed whip damage, caused by nylon string trimmers, which can appear as bruised or torn tissue in the bark. This is an all too common threat to trees, and with thin-skinned species such as citrus, birch, ficus, and camellias, as well as with almost all young trees, weed whip damage can often result in their death, as the flow of water and nutrients is cut off by the disruption of the cambium layer.
No tree benefits from a tourniquet around its trunk, which is why we look for tree stakes and ties that have been left too long and are interfering with the tree’s expansion. Staking assists in the critical establishment of many trees, as it protects them against wind damage for the first year to a year and a half after planting. Once the tree is established, stakes and ties often inhibit its development by preventing the natural swaying that enables the trunk to expand and thicken. Stakes and ties also can cut the circulation in the vascular system as the tree expands around them.
Inspect The Bark
The condition of the bark is another indicator of the health of the tree. Bark loss is a sign of decline and indicates an interruption of the vascular supply. It can be caused by damage to the root system or improper pruning.
There are some trees such as eucalyptus, birch, and Chinese elm, that peel superficial bark naturally, which is why it is crucial to identify your trees and know their characteristics in order to observe them properly. Healthy bark has a firm attachment to the tree and shows and shows good expansion with fresh deposition of tissue, an indicator of the tree’s vigor.
As the examination moves up the tree, the condition of the leaf is another gauge of the tree’s vitality. Healthy leaves are bright, fresh, and hydrated. Curling indicates an insufficient supply of water, while yellowing leaves often indicate a nutrient deficiency. While the loss of leaf in the interior of the tree is a natural part of the tree’s development known as shade out die-back, dead leaves at the tips of branches are a sign of decline in the tree’s health. This is another condition that can be caused by root damage or improper pruning.
We can observe the effects of improper pruning in the tree’s scaffold and canopy. Does the tree have a natural and pleasing form, consistent with its genetic morphology, or has it been forced into unnatural form by topping, hedging, and stumping cuts? Trees with single leads such as pines and cedars should not be given topping cuts, while multiple lead trees can be pruned back to new laterals and new leaders if done properly. Does the tree have natural terminals or is the form of the branches interrupted? How much of the tree is thriving, and what percentage is declining?
By following this method of observation, you can assess the health of your trees, and identify the forces that are interfering with their natural vigor. Even if you can’t identify the causes of decline yourself, an arborist may be able to help you find the source of the tree’s problem without even coming to the site if you have answered these questions carefully. While we can’t answer “What’s wrong with my tree?”, we can help empower you to answer the question yourself. The more you know about your trees, the healthier you can help them be.
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