Question
Hi, Jim
We are building the house in Denver. In order to save 40 feet tall ponderosa pine we moved the house in the convert as far as possible, but in the process of building the ground around this tree was raised  so about 4 feet of the trunk are covered with soil. should we dig it out and surround wit protective net, or just live it as it is?  I am afraid, we are going to kill it after all the effort...
Thank you very much
Lenny

Answer
Tree roots develop and survive where there is adequate oxygen and moisture. Most active tree roots are in the top 3 feet of soil; the majority are in the top 12 inches. The more compacted or poorly drained the soil the closer the roots are to the soil surface. Roots normally grow outward to about three times the branch spread. Only 50 percent of the trees root system occurs between the trunk and the dripline. Roots on one side of the tree normally supply the foliage on the same side of the tree. When the roots on one side of the tree are injured the branches on that side of the tree may die back or die.

Even a few inches of fill or soil removal can cause extensive root damage.When soil air is decreased by filling, certain gases and chemicals increase and become toxic to roots. Symptoms may appear within months or years after filling has occurred. The extent of injury from filling varies with the species, age, and condition of the tree; the depth and type of fill; and drainage. Beech, dogwood, most oaks, pine, sugar maple, spruce, tulip popular, and walnut are the most easily injured. Elm, locust, pin oak, sycamore, and willow are the least effected. Clay soils cause the most damage because the fineness of the soil shuts out air and water more than a gravelly or coarse soil. Three to four inches of soil can be added to small areas under the tree provided the soil texture is coarser than the native soil. Finer textured soils should not be used for filling.

The base of a tree at the soil line should flare out (be wider than the tree trunk a foot above the soil line). If the tree does not have a flare, but enters the ground in a straight line, fill dirt has been added. Digging will reveal the depth of the fill. Other visible symptoms include small leaves, many dead twigs, and the presence of numerous suckers along the main trunk and branches. If the filling was recently done and roots have not begun to regrow into the fill, efforts should be made to restore the soil to its original level.
What you are going to need is to build a tree well around the tree out to the drip line of the outer branches. This will have to be dug to the orginal depth of the soil around the tree. This is a major job. I would suggest you contact the Colorado State Forestry agency and ask for help. There state office contact information is
Colorado State Forest Service
Campus Delivery 5060
Foothills Campus, Bldg. 1050
(Physical Address: 3843 Laporte Ave.)
Fort Collins, CO 80523-5060

Email: [email protected]