Look Up Before It Falls Down

Many tree failures, such as broken limbs and blow-overs, occur during winter months. That’s because rain and wind can be hard on trees.

The good news is that many hazardous situations can be prevented simply by looking up.

“Inspect your trees before and after storms, and you can often spot common structural defects that can be corrected before they cause damage or injury,” said Larry Costello, environmental horticulture advisor for the University of California Cooperative Extension.

Trees are most likely to blow over after substantial rains, which saturate the ground, and then winds, such as the Santa Anas, which can uproot them. There were many tree blow-overs during El Nin~o. With drier and windier conditions, there are more broken branches.

“Generally, the older the tree and the more disturbance that has gone on around the tree, the more likely the tree will be to have problems such as uprooting,” said Tustin registered consulting arborist Greg Applegate.

Many tree failures come as a shock to tree owners.

“We’ve had many people tell us that they were surprised, because a tree looked very healthy before it fell over,” said Costello, who is the co-author of “Recognizing Tree Hazards, A Photographic Guide for Homeowners” (University of California Agriculture and Natural Resources, 1999, $4).

“The truth is, a tree can look and be healthy but can also be structurally weak and prone to failure. On the other hand, some unhealthy trees that don’t look well pose no risk. Don’t conclude because a tree’s leaves are green and the canopy is full that it is structurally sound.”

How a tree becomes structurally unsound can vary. Sometimes trees develop structural defects because of poor early pruning practices. Heading back a young tree, for instance, results in several branches developing from one point on the stem, which can cause branch failure later on. From early on, many trees experience inappropriate pruning, which causes them to regrow in a structurally unsound manner.

Poor root formation will cause problems later, such as uprooting. And even trees with healthy roots can experience problems if work is done in the root zone, such as installing irrigation lines or a swimming pool. Cutting roots often affects the anchorage of a tree and increases the potential for a blow-over.

Look for the seven main problems below when examining your trees for structural soundness. If you spot any trouble areas, call a certified arborist for assistance, especially if the tree is large. Avoid working on the tree yourself, and never climb up into the tree, as this could lead to serious injury. And always consider nearby power lines.

It is generally best to hire an arborist who is certified by the International Society of Arboriculture (ISA) or a consulting arborist who is a member of the American Society of Consulting Arborists (ASCA). Also make sure that your arborist is insured.

Though some of the following situations unfortunately result in tree removal, other problems can be solved and the tree saved. The key is early detection.

Leaners

A tree that has suddenly started leaning requires immediate action. “Leaners are actually trees that are in the process of falling over--they simply haven’t gone all the way, but could do so at any time,” Costello said.

With a leaning situation, the ground is lifted on the side opposite the lean and the roots might be exposed. Typically leaners are the result of a loss of anchorage. The root system is not providing the structural strength needed to hold the tree in an upright position.

While waiting for professional assistance for your leaning tree, look to see whether anything would be damaged if the tree were to fall and if possible, move those items to another area. Keep people, pets and vehicles away from the tree.

“Hazardous trees can be very dangerous,” Applegate said. “There have been many cases of people killed or permanently paralyzed by hazardous tree situations such as falling limbs and blow-overs.”

This scenario only applies to trees that have recently started to lean. Some trees don’t grow vertically but aren’t unsafe.

Multiple Trunks

Some trees develop more than one trunk, which is a condition arborists call “co-dominant stems.” Frequently, the two trunks are weakly attached and prone to splitting apart. This is particularly dangerous in large trees. For trees with co-dominant stems, inspect the point where the trunks meet. If there is a split below that point, the tree has a high potential for failure.

Weak Branches

Examine large branches at the point at which they attach to the trunk. If a split exists in the branch, it’s highly likely that the branch will soon fall. Sometimes weakly attached branches separate partially from the trunk before falling off. Such branches should be removed before they cause damage.

Decay and Cavities

If you find decay or cavities in your tree, don’t make a hasty decision. Some trees live for years with decay. Where the cavity or decay is located will determine how much of a hazard it is.

Decay where branches meet or at the base of a tree is more dangerous than decay in other areas. The presence of mushrooms and conks (bracket-like growths) growing on the bark indicates root rot or wood decay. Only a professional can determine what action is best.

Cracking

Inspect the trunk and large branches for cracks. Cracks can run with or against the grain. If a crack is found, determine whether it extends into the wood or is confined to the bark. Cracks confined to the bark are usually not a problem, but a crack that enters the wood is a reason for concern.

Insert a pencil or similar object into the crack and measure its depth. Generally, if the crack is more than 3 inches deep, it is most likely extending into wood. In some cases, corrective pruning can be done on the tree to reduce the weight and pressure on the branch or trunk.

Hanging Branches

Hangers are branches that are broken but have not fallen from the tree. In some cases they are still partially attached or lodged into another part of the tree. Inspect the tree canopy for broken branches and remove them right away, as they could fall at any time.

Dead Branches

Dead branches will eventually fall off, and large ones are dangerous. Examine evergreens for dead branches at any time of year. Deciduous trees are best checked when they are in full leaf late spring through early fall.

* For a copy of “Recognizing Tree Hazards, A Photographic Guide for Homeowners” (publication No. 21584), call (800) 994-8849.

* The International Society of Arboriculture in Champaign, Ill., can refer you to a certified arborist in your area. Call it at (217) 355-9411 or search for an arborist in your area at https://www.isa-arbor.com.