2     May 12, 2008 - 11:27am | jbaldwin

Re stripped bark on May Day

Re stripped bark on May Day trees: My two big choke cherries suffered severe bark stripping by the moose about 6-8 years ago and I didn’t expect them to survive, but they did. One major branch grew very weakly the following summer, but seemed to revive the following year. Until the bark stripping, these trees did not sucker. Apparently the stress of the bark stripping injury triggered a survival mode and the suckering began! About two years after the bark stripping, CEA removed about 25 percent of both trees they felt were threatening the power line: further stress and increased suckering. I’m going to try a stop suckering product this year to see if it reduces the suckering. The trees will go, but not this year.

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  1     May 8, 2008 - 6:12pm | monsen

Tree Repair For Girdled Trees

If you want to try an extreme method in an attempt to save these trees, a bridge graft may be possible. The University of Minnesota Extension Service has a good description of the proceedures.

Link to their site->
http://www.extension.umn.edu/distribution/horticulture/components/DG0532c.html)

copy/paste from their site without figures->

The Bridge Graft
When the bark of a tree is removed (girdled) completely around the trunk, that part of the tree above the damaged area will die. Even though completely girdled, some trees may leaf out and remain alive for one season, but both the top and root will die the second year unless shoots have been produced below the girdled areas.

Girdling can be caused by rodents, which damage many fruit trees each year. Occasionally a tree may only appear to be girdled if the gnawing has not gone through the bark to the wood. Sometimes the girdled area extends less than halfway around the trunk, and such injuries are protected from drying out, new bark will grow from the cambium. As soon as you discover an injury, cover it with an asphalt grafting compound.

Rabbit damage is usually some distance above the ground or snow line. These animals cut off twigs and pull off bark in shreds. Mice work near the ground out of sight under grass or snow. They usually begin at one spot and enlarge it. Pocket gophers gnaw off roots below the ground. Trees hurt in this way often tip over and cannot be repaired.

The following supplies are necessary to repair girdled trees:

A sharp knife, such as a good jackknife
Small nails for tacking scions to the tree
A light hammer
A nail set
A saw for trimming old thick bark
A shovel or trowel if damage is below the ground
A heavy scrub brush for cleaning excavated bark
Dormant or fresh cut scions for bridges
Asphalt grafting compound or asphalt wound dressing
Scion—Scions for apple trees may be taken from any hardy cultivar of apple or crab apple. Pear scions must be used for pear, plum for plums, and so on. Old trees rarely produce good scion wood unless they were pruned well the previous year. If 1-year old-wood is not available, 2-year wood may be used. If you can anticipate the need, you should cut the scions before any growth begins. Keep them in moist and cool storage. You may cut the scions, fresh as needed, if you bridge promptly before shoot growth begins.

Small Tree—Apple and pear trees under 2 inches in diameter are too small to bridge. The swaying of such small trunks by strong winds will dislodge the scions. If the tree is under 1 inch, it is best to saw it off just below the girdle, then cover the cut with asphalt wound dressing or grafting compound. Shoots of the same cultivar probably will grow out from above the place the tree originally had been grafted. Trees between 1 and 2 inches can best be treated by cutting or sawing them off below the injury in the spring and placing scions in the stubs by cleft grafting. Cherry and plum trees usually are not bridge grafted successfully. If they are only 2 or 3 years old, cut off below the injury and a new shoot will grow out from above the place where the tree originally had been grafted.

How To Bridge Graft—Bridge grafting is done in the spring after growth has started when the bark of the tree to be repaired will lift readily (slip) from the wood—usually between April 15 and May 15.

The first step is to trim the bark of the girdled trees both above and below the girdle. Cut back damaged or frayed bark an inch or so to sound bark. The edges should be clean and smooth. Scrape down old rough bark to live bark.

Two methods of setting scions are used: (1) the L-cut, best for trees with thin bark, and (2) inlay, for trees with thick bark.

To make the L-cut, start at the edge of live bark and cut a slit about 2 inches long in the bark below the girdle (left side in Figure 8). Lift the edges with a dull smooth tool. Such a tool can readily be shaped from hardwood or a piece of plastic. The rat tail of a comb is good for this purpose. Do not use the scion to lift the bark.

Figure 8. Two methods of bridge grafting (L-cut on the left and inlay on the right) are shown. The scion on the left is inserted under the bark at each end; the scion on the right is laid in a groove at each end.

Prepare a second slit at the upper side of the girdle directly above the first.

Shape the scion on the lower end and measure against the girdle to determine the length of the scion. Shape the upper end of the scion to a definite taper with a longer flat surface next to the tree. Slip the ends under the bark, nail them in position and nail down the flaps of bark. In nailing either scion or bark, use care to avoid crushing the bark. A nail set will help to avoid injury to the bark.

The inlay method (right side of Figure 8) is the best bridge grafting technique. In fact, it is a necessity for a short span. Select a curved scion to make an inlay bridge. Measure the distance to be spanned and make the scion long enough to extend 1½ to 2 inches beyond the girdle at each end. Cut a straight, smooth face on each end.

Place a nail in each end. Tack this lightly to the tree bark to mark the place. Mark around each end on the bark to get the exact size of the scion. Remove the scion, cut to the wood on the marks, and lift out the piece of bark. Then fit the scion in the channels in the bark and nail carefully. One nail is usually enough.

In either grafting method, place a scion every 1½ to 2 inches around the tree.

There is a third method to insert scions in bridge grafting, as shown in Figure 9. Little or no trimming is done to the bark that borders the damaged area. This is a little less tidy and it requires somewhat longer scions, but it is quicker and equally effective.

Figure 9. A quick way to bridge girdled trees.
Scions are cut and inserted essentially the same as in Figure 8.

Covering and care—When all the scions are in place, the graft unions should be covered with grafting compound. Note that the entire girdled surface should be covered and more than one coat may be necessary.

In bridge grafting, after the scions begin to grow, it is important that all shoots or leafy growth be cut or rubbed off the scions.

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