Growing Concerns 583: Solving mystery of tree death

Late Summer!

A long backward look can reveal answers when a big tree dies


Dear Janet,

I live in an older neighborhood with mature trees on my lot, including four mature beech trees.

Three years ago I lost one beech near the road and now one of the four remaining trees (again, near the road) is showing signs of decline.

Samples sent in reveal no parasites or other specific problems. I have been told that beeches are sensitive to traffic vibrations from a road and this may be the cause of the loss. The beeches in good health are farther from the road.

Because of the privacy afforded by the beeches' low branches and to maintain some continuity on the lot, it would be nice to replace the lost beeches with new mature ones. But in view of the proximity to the road, should replacement with beech trees be ruled out?

If you advise against beech trees are there any other trees that you would recommend that have low branches like a beech and would do well near a road?


Dear J.M.,

You're right to hesitate before replanting a species that failed on your site. However, I'm surprised you'll consider buying a large, expensive tree without calling in an arborist to assess the situation.

Until you determine what killed one beech and ails the others, any choice is a gamble. The problem might be beech-specific but could be broader, with a negative impact on low-branched alternates such as basswood, pin oak, bad cypress or dawn redwood.

Beeches do have sensitive roots, more likely to rot than recover from being crushed or cut. Yet it's unlikely that road vibrations would affect a beech without similarly affecting other trees along that road.

What happens to soil near strong vibrations --imagine jack hammers and pile drivers -- is that it becomes compacted. It's comparable to what happens during shipping to goods in boxes marked "some settling of contents may occur." Oxygen is what's lost in the settling, yet a free flow of oxygen is vital to roots. Some tree species fail in compacted soil, others tolerate it, but all show some effect

When a big tree fails in ways noticeable to an untrained eye it's usually years into a problem. The tree's reserves may have carried it for a decade or more, masking the decline.

I don't question the results you received from your samples. Trees in decline from environmental stress frequently have no significant pests or diseases. Pests that are present may be secondary to the wasting, opportunists exploiting a weakened host.

An arborist will probably look at your beeches' growth rate for the past five to ten years, seeking signs of when the trouble started. In that discovery may be keys to a solution. As an example, if a tree began struggling in the year a new driveway was installed, providing extra water and fertilizer to the undamaged portion of the roots may speed its recovery.

Short report

Many big trees are stressed this year...

...from oaks and red maples so pale as to be golden, to silver maples thin enough to see through. Here's how to assess a tree's growth rate and determine when the trouble began.

Examine an upper branch or a horizontal limb that extends to the drip line.

Measure how far it grew this year:

- Find the terminal bud at the branch tip, enclosing 2005's shoot.

- Find the terminal bud scar that marks the start of growth this spring. On a beech and many other trees that form terminal buds, this bud scar is distinct and enduring. Look for closely spaced ridges that encircle the twig like a turtleneck.

- Measure back from the terminal bud to this spring's terminal bud scar.

Next, determine and record past years' growth. Measure between each terminal bud scar and the one that preceded it.

Record several branches' growth history. Calculate annual averages.

Look for coincidences between tree growth and changes in the environment.

Compare your tree's growth to its species average, as listed in a book such as Michael Dirr's "Manual of Woody Landscape Plants." Uppermost branches should meet the species average. Lower and inner limbs will grow more slowly.

A beech like those in today's question might have this history:

2004: 7.5 inches, respectable for a beech's lower limbs, although upper branches should grow 12 to 18 inches per year.

2003: 4.375 inches

2202: 3.25 inches

2001: 3.75 inches

2000: 2.375 inches

1999: 0.125 inches

1998: 0.0625 inches

1997: 0.1825 inches

1996: 3.125 inches

1995: 2.5 inches

1994: 0.1825 inches

1993: 4.625 inches

Considering its history, this tree is not in decline but recovering from something that occurred in the mid-1990's.


Green thumbs up

to planting spring bulbs deeper than you ever imagined they could be. Tulips and daffodils planted ten to twelve inches deep are safe from digging animals. They also emerge a bit late in spring, less likely to be harmed by spring frost.


Green thumbs down

to abandoning your annuals now. Those like salvia, petunia, snapdragon and geranium that can handle cool weather will shine into October if you keep deadheading, watering and fertilizing.


 Original publication 9/11/04