Repairing Tree Wounds. Part 3
Crotch hollows also come under the heading of wound repair. Many otherwise well-formed trees (particularly yel-lowwoods) develop deep pockets where their leaders, especially large multiples, branch out from the trunk. In these hollows, which resemble inverted armpits, not only water but fallen bark and wind-blown soil can accumulate. Often parasite plants or seedlings from the tree itself will start growing there. Danger arises from wet-rot and frost pressures. Averting such pockets early in a tree's life or altering them after they have developed is not difficult. The problem involved is purely one of drainage. An open channel can be gouged, or a tube inserted, to the crotch hollow's lowest point. To keep the pocket from collecting debris, fit a sheet-metal cap over it. This can be done also over cavities, to keep out squirrels and such. The tree will accept the shield, with a callus roll, as part of itself if you trace back the bark to open a ledge of wood and tack the metal to it.
Crotches forming a wide angle are always stronger than acute-angle or V crotches. Often the latter look strong because they appear to be reinforced by a roll of callus. But that roll was formed, on the outside only, after that crotch was cracked or actually sprung open some time ago by heavy pressure, as of wind or snow, applied to the member aloft. Unlike a metal joint mended by arc welding it is not "stronger than ever" after its healing, but highly prone to refracture in another big blow or snow. It is particularly important to inspect trees near architecture or over driveways for V crotches, callused or otherwise, for they are inherently weak and hazardous. In trees small enough to handle himself, the home owner can reinforce a faulty crotch in one of two ways, or both; rodding and/or cabling. The rodding mentioned above for reinforcing deep cavities is called "wood screw" and it comes in various diameters up to two inches. It is iron bar, threaded its whole length, which is screwed through opposed holes in the hollow tree and sawed off flush to the bark, which will grow over the ends.
When wood screw is used to reinforce a weak crotch, the crotch should first be drawn together tightly by a "come-along" (interlooped rope sling, or noose) rigged high up in the members forming the crotch. This is necessary because the bar's threading, being continuous, has no pulling power. Turned with a pipe wrench through holes bored slightly smaller than its own diameter, the rod only holds fast in whatever position it is left. More positive in their action, but more expensive, are bolt-and-nut assemblies which must be measured, cut, and threaded to fit each situation. And the nuts, with elliptical or diamond-shaped washers, must be countersunk into the bark to get them healed over properly. But bolts are best for mending split limbs, which they can draw together. The optimum position for rodding is about twice the smaller member's diameter above the weak crotch. In case of dire weakness, put one or even two more rods a like distance farther up. (Always coat with tree paint any metal put into living tree tissues. This goes for drain tubes or pipes, too, which need not be driven more than three or four inches into their holes.)
Cabling to support weak crotches, or to brace any of a tree's upper parts by fastening
them to other parts, is done with galvanized twist wire in gauges that run from 4- to
7-inch. The cable is fastened to hooks or eyes that may be of the lag (screw-in) or
bolt-and-nut type. Loops in the unraveled cable's ends are fashioned by wrapping its
separated strands back around itself with pliers. Cables should be installed while trees
are in leaf, so that tensions can be properly adjusted, again using the "come-along" to
ensure tension enough. The hook or eye should be placed at one-half to two-thirds of the
weak member's length above the crotch. The cable should run upward at about forty-five
degrees to another hook or eye in the supporting member. (In cabling a tree's tops
together for mutual support, this angle can be much less, or even horizontal, the main
thing being to oppose weights and stresses judiciously.) A composite of noosing, cabling,
and rodding a weak-crotched tree is shown in Fig. 12.
Under no circumstances should trees or their members be braced by passing wires, cables,
or chains around them. No matter how you stuff or baffle the collars, sap circulation will
suffer. When a small tree blows over, you can pull it erect with a rope and prop it there
temporarily, to keep its roots underground, with a padded board nailed atop a post. To fix
it permanently erect, don't use the time-honored makeshift of guy wires passed through
hose. Put a screw hook or eyebolt into the trunk about halfway up and run a cable down at
forty-five degrees to a "dead man" buried in the ground. This is a heavy pipe or post,
not driven at a slant but laid horizontally at the bottom of a yard-deep "grave," which
you dig at right angles to the trunk on the windward side. Pass the cable to the "dead
man" through a slanting hole which you poke with your punch-bar, to avoid loosening the
earth between tree and grave. (See Fig. 13) Once they have been blown over, resurrected
trees are likely to go down again if another blow comes before they are securely rerooted.
To guard against this, in case the next gale should come from a new angle, put in two or
three cables to buried anchors.