Consider the Root Zone

ChiloquinNews article 9/5/2011

I’ve been over in Phoenix (that’s the Oregon Phoenix, near Ashland) this weekend, mulling over what to do about a lovely Western Redcedar (Thuja plicata) growing in the front yard of the tiny house we have there. Besides having quite a lean, it has a lot of brown foliage which has fallen and covered the sidewalk.  It’s an interesting problem, because it’s related, I think, to the problem that an aspen tree is having right here in Chiloquin in a friend’s yard. The aspen began to lean last year, and now is in need of bracing to keep it upright. Aside from that, it looks quite healthy.

 I believe it’s the roots that are in trouble with both trees. Roots are one of the most vital parts of a tree. They are responsible for nutrient and water uptake, they store energy, and they anchor the plant. Trees are never the same shape below ground as they are above, so it is difficult to predict the length or location of their roots. Typically, though, approximately 90-95 percent of a tree’s root system is in the top three feet of soil, and more than half is in the top one foot. The “dripline” is defined as the area directly below the branches of the tree. However, many roots extend beyond the longest branches a distance equal to two or more times the height of the tree.

Western Redcedar is found on the coast from southern Alaska to northern California and also in the Rocky mountains from Alberta to Idaho and Montana. In addition to growing in lush forests and mountainsides, Western Redcedar is also a riparian tree, and grows in many forested swamps and along stream banks in its range, and can even stand in some water in the winter. The extreme of very wet conditions in the fall and winter, followed by a hot, dry summer, is very stressful for the roots. Although the trees are very different in appearance above ground, the same is also true of aspen roots.

The aspen is growing alongside a driveway that is not watered, and another section of the root zone is below a rocky area that is also not watered. Just one little pie-shaped slice in the aspen’s root zone gets water in the summer. The Western Redcedar is growing in suburbia. It has a house on one side, a road on the other, and a paved driveway on the third side. Just one little patch of garden gets water in the summer, and worse for the Redcedar is that even in winter not much water reaches most of the root zone. The aspen does at least get a good soaking in winter.

The solution for the aspen is relatively easy. Water the gravel driveway and the rocky area, and the roots should get stronger over the whole root zone. The Redcedar poses a bigger problem. Nothing can be done about the house and the road that are squeezing in from each side. The town of Phoenix compounded the problem by installing concrete sidewalks in a beautification program a couple of years ago, further reducing the amount of permeable ground around the tree. We have decided that our only option is to remove our small section of paved driveway and replace it with permeable pavers.

Permeable paving is becoming a popular thing to do in areas where runoff is contaminating ground water. It is mandated in places like Lake Tahoe. Instead of running off into storm drains, rainwater can percolate down through the paving into the soil below. It might be costly but may mean life for our Redcedar. It would be just as costly to have the dead tree removed, and much less satisfying.

I guess the moral of this story is to think about the roots as well as the canopy when planting a tree. Our Redcedar may have been planted by someone who could not have known that the lot would be divided, and a house and driveway built around the tree, or it could have been a volunteer seedling that was left to grow. Whatever its history, intervention is needed now to keep it alive and healthy.


House on one side, road on the other, pavement on the third. Just a tiny patch for water.



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