Thursday, September 04, 2008
Look for these warning signs in maple trees
John Arbogast
Landscape consultant John Arbogast answers your questions every Thursday. Send questions about your lawn, garden, plants, or insects to:
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Roanoke, Va. 24018
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Q: We need your opinion on what we should to or with two old maple trees on property that we now own. We’ve gotten opinions before, and no answer regarding these two old trees is agreeable to everyone in the family. Both maples have smaller than normal size leaves and more and more dead branches. One maple is surrounded by grass and ivy and is about 12 feet away from an old house on one side and about 1 foot away from a hedge and wall that goes down to a concrete walk and paved street. There are big side limbs that hang over the house on one side and over the street on the opposite side. These two big side limbs were cabled together several years ago. This maple still gives nice shade, but there is a lot of decay in the upper portion. The other old maple is not surrounded by grass, since it is fairly near a parking area from which guests walk over. It has several big branch intersections that are in the shape of a “V”. Some of us were amused that weeds are growing in the bottom of each “V”. What should we do? This second maple gives nice shade too, but it looks sick. Its leaves are a little bigger than the first maple’s, but some of the leaves have yellow and brown edges.
A: Your nice verbal description gives a good picture of two old trees that might be difficult to part with but they both pose risks that could be unreasonable to solve. Let me briefly give details for “red-flag” things to look for to help come up with an agreeable decision to remove trees now or later.
The smaller than normal leaf size indicates that a tree is weak due to a long list of possibilities that include insufficient roots, injuries, inadequate water, reduced natural sugar production, absence of sufficient air in a compacted soil, and more. Progressive reduction in leaf size will mean that the afflicted tree will starve eventually, as the leaves are nature’s chlorophyll factories that conduct photosynthesis to produce natural sugars that are a tree’s food.
Decay in a tree causes the tree to lose structural strength and can pose a hidden risk. Even the cabling that you mentioned does not guarantee stability forever. Cabling and bracing can help, especially if there are multiple cables/braces rather than just one. However, if water, snow, and/or ice can enter decayed areas through wounds and cracks, further decay will occur at a faster rate. Trees naturally work to wall off the spread of decay, but continued moisture causes the tree to lose the battle.
Decay in a tree is a hidden risk, since we can’t see how much hollow heartwood is gone as decay or composting eats up the tree’s core. Extensive decay to an insurance professional means that a tree must go, but a gambler might see decay and say let’s enjoy the shade and hope that no one is on the nearby sidewalk or driving on the street under that one branch when it crashes down.
Continued dying of more and more tree branches simply tells us that the afflicted tree cannot provide water and dissolved nutrients to those areas for whatever reason. Removing dead branches as needed is good sanitation, but that doesn’t solve the problem that is preventing the tree from absorbing, moving, and distributing ample water and nutrients. Applying nutrients over a tree’s root area might make the owner(s) feel good, although it doesn’t solve the problem that could exist with the tree’s distribution system.
Consider in making your decision the reduction in the water table if these maples are located in one of the drought areas of the country in deciding what to do about the maples. This is related to the continued branch dieback mentioned above. The maple that has grass, ivy, and the hedge under its branches must compete with those plants for rainwater. The fact that this maple is 1 foot away from a wall cut down to a lower sidewalk and street means that the tree has no feeder or anchor roots on that side. The other maple that has only gravel and soil under its branches in an area that serves as a visitor walkway from the parking area indicates that the soil around this maple’s roots is probably compacted and thus doesn’t have many soil pore spaces for water that roots can absorb.
Another thing that would make me worry about the risk posed by the second maple is the number of “V” shaped limb and trunk intersections there. “V” shaped crotches, as they’re called, become structurally weaker as a tree grows, since you have limb bark pushing against trunk bark as they both grow in diameter. This is just not strong compared to a connection of wood joining other wood.
The humorous thing of weeds growing in those “V”s indicates damp compost or decay in those intersections. This is not good.
The yellow and brown leaf edge appearance on the second maple is called scorch. This is a symptom of a lack of water and could be caused by anything from dry soil; root problem such as insufficient roots to compacted soil caused by foot or vehicle traffic; to declining tree vigor.
