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The root of the matter || Thousand Oaks Acorn

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The root of the matter

38p1.thumbnail.jpgThe environment of a tree is the environment of a tree. I know that sounds redundant—and it is. But when you digest that sentence and insert it into the context of where a tree grows and what goes on around that tree, it might make a little more sense.

I recently returned a call from a man in Simi Valley who answered the phone obviously out of breath. He’d been in his backyard digging for hours in the hot sun, trying to find the root flare of the mighty 400-year-old oak tree along his back wall.

The term root flare, also called a basal flare, is the point of a tree near the soil level where the main stem begins to transition into the root system. At this spot, the main stem begins to flare out at the soil surface to accommodate the expansion of the roots.

The ancient valley oak that he was digging around is one of several oaks on his large piece of property. Someone observed that the main stem of that particular oak tree appeared to have no root flare at all, and in fact looked like a large telephone pole just stuck in the ground.

The homeowner had done no work around the tree since moving into his house almost 10 years ago, so he knew it was nothing he did that caused a change to the level of the soil near the tree. And so began the enigma.

Looking further into the matter, he discovered that the buildup of soil around the base of the tree, hiding the root flare, is not healthy for the tree. Armed with this information and a shovel, the man began to dig and dig, but at 2 feet down he’d still not found the root flare. It was around that time he called me asking for advice.

While digging around the tree, he said, he was running into a lot of small roots—some even an inch in diameter—that appeared to be growing out of the trunk of the tree. I asked him if he’d seen any indication that he was near the flare of the root system, and when he said no, I suggested he stop trying to find the root flare and carefully put the dirt back in the hole.

Why did I tell him to go against all tree healthcare logic and replace the dirt? Because the environment around that tree had become the new acceptable environment for that tree.

When you buy potted tomato plants from the nursery, the best way to get them to grow quickly and strongly is to plant them deeper in the soil than they come in their pot. Soon after this deeper planting, they grow adventitious roots out of the main stem.

With a tomato plant, this is good and normal, but with a tree it is not. When this oak tree was backfilled, it began to grow adventitious roots just like a tomato plant does, and most likely it is deriving some sort of nutrition and water from the new roots.

I told the man my concern is that the tree may have grown these unusual roots out of necessity due to stress, and cutting them may in fact do more harm than good.

Unfortunately, many tree species cannot and do not adapt to adverse change in their environment and quickly die. But some mature native oak trees have the ability to adapt to some change in their surroundings and continue to live with acceptable health for quite a long time.

I’ve observed many dozens of native oaks more than 300 years old that are still living in man-made conditions that would kill most other trees. Backfilling around the trunk is just one example, but there are more.

In many local areas are oaks that appear to be in deep wells, surrounded by a circular block wall and covered with latticework. The soil around the tree was actually raised for development and the well was constructed to keep the backfill away from the trunk.

Still, with all the compacted soil covering the roots and many of the wells filling up with rainwater in the winter, most trees would not have survived more than a year or two. But many of these oaks are still alive 40 years later.

Though every effort should be made not to change the growing conditions around a tree, sometimes it’s been done before we came along and we have no control over that change. In the case of the oak tree with the backfill and adventitious roots, if the tree still looks healthy, it’s best to just leave it alone.

The new environment the tree is living in is its new acceptable environment, and if the tree can live with it, perhaps we should, too.

Mortimer is a certified arborist with more than 30 years’ experience in the tree care industry. Email questions to dmortimer.

2012-09-20 / Columns


Written by vaphc

September 20, 2012 at 3:16 pm

Posted in Uncategorized

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