Check tree for trouble

If a tree or shrub behaves in an unusual way, such as to develop fall color early, shed leaves in summer, etc., it may be saying "I need some help, here." So give it a good look.

Things to check:
     Growth rate
     Leaf/wood appearance
     Environmental change
As an example, we investigate an oak's odd behavior

First, check its growth rate.

Do that by comparing it to:

  • The lists below,
  • What your plant encyclopedia states is normal for the species, or
  • A healthy plant of the same species and type.

Any sharp decrease in growth rate or steady decrease tells you to keep looking and identify the cause. (In the example at the end of this article and in What's Coming Up 50, we demonstrated reading the branch to measure the growth rate.)

Tree and shrub growth rates

  Growth rate
Slow growing tree or shrub Less than 6 inches per year
Average growing tree or shrub 6 to 12 inches per year
Fast growing tree or shrub +18 inches per year
Miniature conifer* Less than 1 inch per year
Dwarf conifer* 1 to 6 inches per year
Intermediate conifer* 6 to 12 inches per year
Large conifer* +12 inches per year

*As established by the American Conifer Society. Refers to growth in any direction. Size may vary due to cultural conditions, climate and geographic region.

Second, check the appearance of its leaf and wood

Compare leaf size, leaf color and color of the new twig, bark, and inner wood). Again, consult plant encyclopedias or compare your plant to a healthy specimen of the same species and type.

If you see differences, use descriptive words and the plant name to Search for possible problems. For example, oak reduced growth rate; maple scorched leaves; linden blackened bark; burning bush distorted new growth.

Third, look at the trunk at ground level

  • Does it flare evenly on all sides or is it flattened on one or more sides?
  • Do you see any roots circling around the trunk or very close outside the trunk?
  • Do you see any physical damage?

Fourth, consider any environmental changes

  • Has there been construction in the area beneath the branches?
  • Has care changed: Watering, fertilizer, herbicide applications?
  • Have activities changed beneath the branches -- more foot traffic, for instance?

If you noted a decrease in growth rate, count backward on the branch and look into changes that happened just before the growth rate slowed.

An exampleSynowiecOakLvsS.jpg

An oak behaved oddly.

Right: One fall, its leaves did not change color and drop, but turned from green to brown and remained attached to the tree. Other oaks of the same kind in the neighborhood did not act this way.

So we looked and found:

The growth rate is very low.

The growth rate was better 4 years ago.

Twigs are thin, not stout as we see in similar oaks.

Below: The arrows point to terminal bud scars -- the mark left circling the branch when growth resumes at the tip of that branch each spring. At far right, note that there is less than an inch of new growth between the most recent terminal bud scar and the tip buds set to begin growing next spring. On the left, further back along that branch at the terminal bud scar formed four springs ago, the space between terminal bud scars increases to several inches.


 Below: A branch of the tree in question (lower twig) compared to another oak that's behaving normally. The other oak has five times the growth rate of our tree.OakTwigComparN5924s.jpg

The leaves have some damage but are fairly normal in size and color.  

Below: The damage might be chewing damage, perpetrated by something that makes holes in the blade, not along the edge. We use a magnifier to look more closely.

OakBrGoodLkN5713s.jpg OakLfRegDmgN5728s.jpg

Some leaves have fuzzy spots where veins meet.

OakLfUseMagnifN5712s.jpg OakLfVeinFuzN5711s.jpg

Branches have dark stain, especially on the upper surface of the lowest horizontal limbs.

Below: Compare the upper surface of a branch (top photo of the two below) to its lower surface. See the dark sooty mold that's grown there? It's a fungus that's consuming insect excrement -- honeydew  -- that rained down there from sucking insects above.


 Below: The sooty mold is worst on lowest branches that have received the most honeydew.


The trunk looks flared on all sides, without physical damage or circling roots. (For why we look at the trunk: Check the excellent illustration of finding an dealing with a girdling root in What's Coming Up #49.)

No construction or changes in care or activity have occurred in the past five years.

There are small pimple-like bumps on some twig ends.

As a result of this investigation, we went searching for oak insect problems that might cause sooty mold, reduce growth rate, involve the tip buds and are present over winter. We found one to watch for.