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:
As an example, we investigate an oak's odd
First, check its growth
Do that by comparing it to:
- The lists below,
- What your plant encyclopedia states is normal for the species,
- 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
Coming Up 50, we demonstrated reading the branch to
measure the growth rate.)
Tree and shrub growth rates
|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
||Less than 1 inch per year
||1 to 6 inches per year
||6 to 12 inches per year
||+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
- 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
- Has there been construction in the area beneath the
- Has care changed: Watering, fertilizer, herbicide
- 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
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
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
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.
The leaves have some damage but are fairly normal in size and
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.
Some leaves have fuzzy spots where veins meet.
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
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
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