Question
Dear Mr. Camper,

I have an old cherry tree. I just cleaned out a large hollow in the trunk. The main branch above the hollow grows in a sickly manner as compared to the branches below the hollow. For example: on the sick branches the leaves are red in fall colors, but are still green on the health branches. Water will collect in this hollow. My question : Can I fill this tree hollow? I would hate to cut away healthy tissue so that the hole drains properly. What material should I use ? I would like to save the tree.

Thank You, Bill

Answer
Hi there. 30 odd years ago when I started we filling cavities.Brick,block concrete any thing we could get our hands on. Than it progressed to an expanding foam. If the client had money we would fill the cavity than do some fancy tile work over the outside.
Things have changed. Scientists have found that there are aerobic and anaerobic decay fungi.One that live in an oxygen or no oxygen environment. In other words if the cavity is wet leave it wet.If it's dry leave it dry. Think about it.How many years does a wooden boat stay  in the water? Sorry about rambling on. BOTTOM LINE.LEAVE THE CAVITY ALONE!!!!!
As for the health of the tree,here is some info you might find useful
Mature Tree Care
Think of tree care as an investment. A healthy tree increases in value with age梡aying big dividends, increasing property values, beautifying our surroundings, purifying our air, saving energy by providing cooling shade from summer's heat, and protection from winter's wind. Providing a preventive care program for your landscape plants is like putting money in
the bank. Regular maintenance, designed to promote plant health and vigor, ensures their value will continue to grow. Preventing a problem is much less costly and time consuming than curing one once it has developed. An effective maintenance program, including regular inspections and the necessary follow-up care of mulching, fertilizing,
and pruning, can detect problems and correct them before they become damaging or fatal. Considering many tree species can live as long as 200-300 years, including these practices when caring for your home landscape is an investment that will offer enjoyment and value for generations.
Tree Inspection
Tree inspection is an evaluation tool to call attention to any change in the tree's health before the problem becomes too serious. By providing regular inspections of mature trees at least once a year, you can prevent or reduce the severity of future disease, insect, and environmental problems. During tree inspection, be sure to examine four characteristics
of tree vigor: new leaves or buds, leaf size, twig growth, and absence of crown dieback (gradual death of the upper part of the tree). A reduction in the extension of shoots (new growing parts), such as buds or new leaves, is a fairly reliable cue that the tree's health has recently changed. To evaluate this, compare the growth of the shoots over the past three years. Determine if there is a reduction in the tree's typical growth pattern. Further signs of poor tree health are trunk decay and/or crown dieback. These symptoms often indicate problems that began several years before. Loose bark or deformed growths,
such as trunk conks (mushrooms), are common signs of stem decay. Any abnormalities found during these inspections, including insect activity and spotted, deformed, discolored, or dead leaves and twigs should be noted and watched closely. If you are uncertain as to what should be done, report your findings to your local ISA Certified Arborist or other tree care professional for advice on possible treatment.
Mulching
Mulching can reduce environmental stress by providing trees with a stable root environment that is cooler and contains more moisture than the surrounding soil.  Mulch can also prevent mechanical damage by keeping machines such as lawnmowers and weed whacker whips away from the tree's base. Further, mulch reduces competition from surrounding weeds and turf. To be most effective in all of these functions, mulch should be placed 2-4 inches deep and cover the entire root system, which may be as far as 2-3 times the diameter of the branch spread of the tree. If the area and activities happening around the tree do not permit the entire area to be mulched, it is recommended that you mulch as much of the area under the drip line of the tree as possible. When placing mulch, care should be taken not to cover the actual trunk of the tree. This mulch-free area, 1-2 inches wide at the base, is sufficient to avoid moist bark conditions and prevent trunk decay. An organic mulch layer of 2-4 inches of loosely packed shredded leaves, pine straw, peat moss, or composted wood chips is adequate. Plastic should not be used because it interferes with the exchange of gases between soil and air, which inhibits root growth. Thicker mulch layers, 5-6 inches or greater, may also inhibit gas exchange.
.Pruning
Pruning is the most common tree maintenance procedure next to watering. Pruning is often desirable or necessary to remove dead, diseased, or insect infested branches, and to improve tree structure, enhance vigor, or maintain safety. Since each cut has the potential to change the growth of (or cause damage to) a tree, no branch should be removed without a reason.
Removing foliage from a tree has two distinct effects on its growth. Removing leaves reduces photosynthesis and may reduce overall growth. This is why pruning should always be performed sparingly. Over-pruning is extremely harmful because without enough leaves a tree cannot gather and process enough sunlight to survive. However, after pruning, the growth that does occur takes place on fewer shoots, so they tend to grow longer than they would without pruning. Understanding how the tree responds to pruning should assist you when selecting branches for removal. Pruning mature trees may require special equipment, training, and experience. If the pruning work requires climbing, the use of a chain or hand saw, or the removal of large limbs, the use of personal safety equipment, such as protective eye wear and hearing
protection, is a must. Arborists can provide a variety of services to assist in performing the job safely and reducing risk of personal injury and damage to your property. They also are able to determine what type of pruning is necessary to maintain or improve the health, appearance, and safety of your trees.
Removal
Although tree removal is a last resort, there are circumstances when it is necessary. An arborist can help decide whether or not a tree should be removed. Professionally trained arborists have the skills and equipment to safely and efficiently remove trees. Removal is recommended when a tree:
?is dead, dying, or considered irreparably hazardous.
?is causing an obstruction or is crowding and causing harm to other trees and the
situation is impossible to correct through pruning.
?is to be replaced by a more suitable specimen.
?should be removed to allow for construction.
With proper maintenance, trees are attractive and can add considerable value to your property. Poorly maintained trees, on the other hand, can be a significant liability. Pruning or removing trees, especially large trees, can be dangerous work. It should only be performed by those trained and equipped to work safely in trees. For more information
on mature tree care contact your local certified arborist.
Hope this helps,Bill