My previous column, ‘Give Them Space’, touched on selecting and planting trees. The typical problem: The tree variety grows too large for the available space.

Now let’s look at the other side of the problem: When our needs and plans intrude on the the space of an established tree.

Here is a classic example, a composite based on actual events I’ve seen over the years: A native valley oak tree grows for 150 years, fat and happy in the countryside. Under good conditions, left alone in a relatively stable environment, it could live another century or two, or more, gradually accumulating the normal trademarks and battle scars of a veteran oak.  As the saying goes, “An oak spends 100 years growing, 100 years living, and 100 years dying.”

Sometime around year 150, plans are made for a new residential street near the tree. Because of property line considerations, the road goes in about       20 feet from the trunk along one side of the root zone.  Soil, which the roots and associated symbionts  colonized for a century and a half, over 2 or 3 acres, is cut away, compacted, graveled and paved.  About 1/3 of the root living space of the tree is gone.

Then, for aesthetic reasons, the border along the road gets landscaped: tilling, trenching for irrigation lines, turf and watering near the tree, which takes away more of its space and turns soil conditions in favor of root disease.

The tree carries on for about 20 years, with no obvious sign of trouble, while its new neighbors admire its beauty.

Around  year 170 for the tree, plans are made for development of custom home sites on the other side of the tree. With the new lot lines, the tree is now on a 10,000 square-foot lot.  The project architect designs a 3,000-square-foot home, which must go in under the branches and within a few feet of the trunk. No tree protection plans are included in the design. Protection is not required on such a small lot, according to the local ordinances.

As construction goes forward, about 99 percent of the original root zone space is now directly altered. Meanwhile, grading equipment needs space to operate around the home site, contractors need space to work, utility trenches  must be dug. 

Overhead, the two-story home will rise well into space long occupied by low limbs, requiring large pruning wounds and the loss of foliage that is necessary for tree health.

Finally, the landscape goes in, providing plenty of greenery and flowers around the outside of the home in the remaining tiny sliver of the root zone.

It all adds up to destruction of the living space of the tree, direct loss of life-sustaining roots, branches and leaves, antagonistic cultural conditions, and infliction of large wounds, which open the tree to decay.

When the home is completed, the tree still has curb appeal. The new owners love their new home, nestled in the oaks. But after two or three or even seven years, outer branches start to die back. Foliage is less abundant and drops earlier than normal.  Perhaps, suspicious mushrooms start sprouting at the base of the trunk. 

An arborist is called in  to examine the tree, the owners pleading: “We need to save this grand old tree! What can we do?”

Do? It’s pretty much done. As Dr. “Bones” McCoy used to say in Star Trek: “I’m a doctor, Jim, not a miracle worker!”

Next time let’s look at a few things that can be done, with a focus on prevention rather can cure.

I’ll be giving a presentation, “Living With Trees in Napa Valley: The Good, the Bad and the Ugly,” at the Napa City-County Library, Sept. 3, at 7 p.m. Admission is free. Come and spend some time looking at local sights. Have a closer look at our local tree-related problems and get some some common sense answers to your questions about trees.

Bill Pramuk is a registered consulting arborist. Visit his Web site, www.billpramuk.com, e-mail questions to info@billpramuk.com, or call him at 226-2884.