Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: SUNDAY, March 10, 1991 TAG: 9103110381
SECTION: HOMES PAGE: B-6 EDITION: METRO
SOURCE: JOHN ARBOGAST
DATELINE: LENGTH: Medium
A: It is true that adding eight inches or more soil over the root system of an existing tree can cause it to die. So, if you want to raise the grade in your back yard and still save those trees, provided that the trees have been in excellent condition already and are worth saving, the answer to your situation is to build tree wells around each tree before filling over their root area. However, constructing tree wells for deep soil-fills such as you may have to do around trees near the 5-foot-tall retaining wall can be a complicated.
Here are some suggested steps to add to the basic tree well, which is suitable where up to about 2 feet of fill is to be used:
1. Pile coarse stones (large size) in a ring over the old soil grade around the tree starting about 3 feet from the trunk, to a depth up to about 8 inches below the final expected soil level.
2. Slope the stone fill down so that it extends out and ends at a distance equal to about three-fourth the mature spread of that tree's branches.
3. Then construct a facing stone wall (kind of construction that will not break up as the temperatures freeze and thaw) to form the "well" around the tree; in order to prevent things and people from falling into that well, the wall can be constructed so a "tree grate" can be placed on top, such is used in some cities where trees are planted on sidewalks. If the coarse fill has spilled around the tree trunks, it will be necessary to pull that back so the wall can be built on the original grade.
4. Fill in with more coarse stones behind the wall to meet the pile formed in step 1.
5. Apply about 2 or 3 inches of crushed stone or gravel over that coarse material. This will allow air to reach the tree roots below so that healthy growth can continue.
Note that the crushed stone or gravel used should have a composition of neutral chemical reaction so that the pH of that soil is not altered as would happen if crushed limestone was used.
Now, here's where the additional work comes in for you. Place 4-inch drain tiles or commercially available black plastic corrugated pipe, which has holes in a connected radiating structural pattern, on the original grade level. Then, some sort of air entrance openings will be needed in the tree well and in the tile or plastic pipe. This will allow air into the new filled surface level to prevent stagnation. Heavy screen wire can be placed over these openings on the new surface to keep out debris, peoples' heels and rodents.
Weigh the cost of doing all this against the expense of cutting down and removing the existing trees, planting new ones and losing the shade and beauty of the established trees.
It may be a good idea to have a professional tree company prune the trees before the wells are built. That will reduce the load on the trees' root systems.
Q: I need something to prevent dogs from urinating on my azaleas. I have three planted in a group. One is already dead, and the dogs are working on the other two. I tried moth balls but it does not work. M.R.M., Stuart
A: There is no special potion or magic solution that will keep dogs away from plants all the time. The only reliable solution may be some sort of physical barrier that will prevent the dogs from getting close enough to do their business on the plants. Commercially prepared dog repellents are available and can offer varying degrees of success. They're worth a try. I've heard others say that mothballs don't work for dogs.
Got a question about your garden, lawn, plants, or insects? Write to Dear John, c/o the Roanoke Times & World-News, P.O. Box 2491, Roanoke, Va. 24010.
Gardener's checklist
Jobs for in mid March:
Early spring is the time to fertilize shrubs and trees that have shown signs of poor growth. Such signs, based on last year's appearance, would be light green leaf color, short thin twig growth, and/or dead branches. Use 10-10-10, 5-10-5, nitrogen-only fertilizers, or special products designed to be dissolved in water. Shrubs and trees that have been making good growth should not be overstimulated by fertilizing.
There's not much time left to plant spring peas, also called garden peas or English peas, in gardens in Roanoke. Gardeners working at higher elevations may want to wait a few more days. Garden peas need to go in early so that they can grow, flower and produce pods before the weather turns hot. Of course, don't till or spade the garden soil when it is wet.
by CNB