EXTENSION REPORT

Baldwin County Office  

302A Byrne Street      

Bay Minette, AL  36507   

Beau Brodbeck                

Regional Extension Agent

Forestry, Wildlife & Natural Resources                  

                                                                                                                                                            May 27, 2008                                                 

Identifying Weak Trees in Your Yard

What’s the first image that comes to your mind when you think, ‘hurricane aftermath’?  Was it devastation with lots of broken and fallen trees and scattered branches?  Trees failing during strong storms are a major source of property damage for the average homeowner.  After all, what grows close by that shades your house/lawn/street and keeps you cool throughout the Gulf Coast summer?

Trees are amazingly long-lived plants, often large and heavy (those trunks and branches are all wood filled with water) and are a study in the physics of balancing forces.  Substantial weights, pressures, and stresses are placed on roots, trunks, and limbs made of green wood.  With hurricane season rapidly approaching now is the time to inspect your urban trees for safety concerns to home and property.  Identifying tree defects and figuring out what to do about it can be very difficult for someone unstudied in tree biology.  Unlike most of the other plants in your yard, trees are very complex and their problems often hidden from view or difficult to assess for health and structural integrity. 

If you suspect a weak tree near your home, hiring a Certified Arborist is often the best decision.  To become a Certified Arborist one has to pass an intensive exam covering 12 domains of arboricultural knowledge administered by the International Society of Arboriculture.  This makes an ISA Certified Arborist a much safer choice for tree work and advice.  Just ask when you call a company if the arborist that will visit you is certified by the International Society of Arboriculture.  Often, Certified Arborists will also feature their certification number or sticker on their truck, calling card, or paperwork. 

The first and best thing to understand about trees is that there is no such thing as a perfect tree.  All trees will have various defects and/or decay that can lead to failure.  Just living long enough to become a big tree usually means that trees accumulate problems, kind of like how we accumulate problems as we age; arthritis acting up anyone? The key is minimizing the risks and as Neil Letson, a forester with the Alabama Forestry Commission explains, “like any other valuable asset, better management increases returns and minimizes risks. “ In cities and suburbs, most trees are street side or near a home or vehicle.  Less risk equals less application for insurance payment or you having to pay for tree removal and major home repairs.

The first step toward having safer trees is being proactive throughout the lives of your trees.   As Letson explains, there are three simple rules towards having safer trees—“systematic inspections, treating problems quickly, and removing a tree when its risks outweigh its value”.  Here along the Gulf Coast the risk of having unsafe trees with structural defects is especially problematic due to high winds generated by hurricanes.

To help you figure out if you have a problem that needs more careful checking by a professional, here are some important key signs that may give away a potentially weak tree.   Always remember to examine every part of a tree, especially a large one; from all available angles and different distances to be sure you’ve looked at the WHOLE tree.  The major parts to examine are the roots, the trunk, and the crown.

First, identify the tree species.  Some species of trees are more susceptible to disease, decay, or structural problems than others.  For example, water oaks, silver maples, and black cherries are fast growing and often become hollow, riddled with decay, and often structurally unsafe as they become mature. 

After identifying the tree species begin by examining the roots.  Root failure is one of the leading causes of a whole tree falling over during a storm.  There are two primary types of root failure: first is soil failure, or soils that lose the ability to hold the root system in place.  Such as saturated soils, which may be caused by overly aggressive watering or areas with poor soil drainage.  Saturated soils when combined with high winds can lead to toppling trees and root failure. Look to see if your soil is continuously wet. 

Secondly, there are root defects.  While root defects may range from construction damage (roots got cut off) to limited growing space (not a lot of room to spread roots out) this article will focus on identifying root decay.  Begin by looking for mushrooms or conks (toadstools or shelf fungus) growing on or near the base of the tree or on the ground under the tree.  These growths are the fruiting bodies of decay and are signs of a serious problem within the tree.  Decay can spread up the truck of the tree and down into the roots causing large hollows.  If conks are seen, contact a Certified Arborist to identify the extent of the decay within the tree to ensure the right management decision is reached. 

Pay close attention to leaning trees, while a leaning tree doesn’t necessarily mean it will fall, “it certainly warrants a closer look”, explains Neil Letson.   Leaning trees may have decay due to broken roots; if no conks are present a good indicator of a problematic leaning tree is a soil mound at the base of the tree on the opposite side of the lean.  This is a common occurrence along Alabama’s Gulf Coast due to hurricane winds.   Leaning trees with mounding often indicates broken and damaged roots and should be examined by a professional immediately.

After a careful assessment of the roots, it’s time to move up the tree to the trunk and branches.  Decay on trees results from some type of injury ranging from an old broken branch or pruning cut to some type of mechanical injury, such as a hitting a tree with a vehicle.  Most trees will have decay or rotten wood somewhere on the trunk, the key is identifying whether it’s impacting the tree’s structural integrity.

The size and location of the decay or cavity will determine if the tree is unsafe. 

“The larger the size, the greater the risk”, explains Letson.  Additionally, the location of the decay such as near a junction of a large branch or near the base of the tree increases the risk.  There are several signs of decay to look for in trees, which include mushrooms and conks, loose or missing bark, dead branch stubs still on the tree, cavities or hollows, carpenter ants or bees, nesting holes, oozing sap or fluids, and trunk bulges. 

Decay within the tree trunk can lead to reduced capacity to withstand the pressure applied by tree weight combined with wind.  If one of the above signs is identified quantifying the amount of decay is difficult and will require the use of specialized tools Certified Arborists can provide.  Indicators of decay such as bulges, oozing holes, and carpenter ants are often all you may see from outside a tree.  In assessing your trees, it’s important to realize that you may have to depend on these more obscure signs, because conks or mushrooms may not always be present.

Next, examine the major branches of your tree.  The same things you looked for on the trunk look for on the major branches with the addition of crotch angles.  The angle at which the branch meets the trunk is extremely important in assessing how strong the attachment is.  In general, but not always, a narrow angle means a weak point of attachment; a wider angle means a stronger attachment.  The problem with narrow crotch angles is that the bark between the branch and the trunk interferes with how strongly the branch is attached to the tree.  Weak attachments could cause branch loss during high winds.

The only tree part we haven’t really looked at is the leaves/needles.  These can really give you a great hint as to the overall health of the tree.  Generally, lots of dark colored foliage well distributed over the whole canopy, and dense enough that seeing through the canopy is difficult, is good.  If you see patchy foliage clustered together or if the leaves/needles are smaller and pale colored you should check the tree over again to see if you missed anything or call on a professional to check the tree for you.

This is a very casual inspection we’ve laid out here, intended to educate, not alarm. Living with trees means getting to know them well and treating them as the valuable assets they are.  Inspect your trees regularly and protect them from undue harm and they’ll reward you with home value, cool the local climate, and improve the quality of life for you and your neighbors.

This article was written in conjunction with Jack Rowe, Regional Extension Agent in Urban Forestry. He works with Extension as an urban forester for several communities in a nine county region in west central Alabama.

Email address: brodbam@auburn.edu

Phone: 937-7176 or 943-5611, ext. 2222

Issued in furtherance of Cooperative Extension work in agriculture and home economics, Acts of May 8 and June 30, 1914, and other related acts, in cooperation with the U.S. Department of Agriculture. The Alabama Cooperative Extension System (Alabama A&M University and Auburn University) offers educational programs, materials, and equal opportunity employment to all people without regard to race, color, national origin, religion, sex, age, veteran status, or disability.

~Back~