Springtime, miracle time.  When you behold the buds and the flowers, aren't you glad you planted this tree last year?

Now, this might be the appropriate moment to point out the following:

MATCHING THE RIGHT TREE WITH THE RIGHT SOIL.  It is important to know the pH of both.  Avoid common mistakes, e-g. planting a pin oak which requires an acid soil (low pH) in an alkaline soil (high pH).  If you do, a host of problems will follow, beginning with the unavailability of iron and magnesium needed for the production of chlorophyll which does the photosynthesis by which carbon dioxide with the help of the sun is transformed into basic sugar.  The deficit is often mis-interpreted as lack of iron in the soil and/or pest or fungus problems.  It should be pointed out that the pH of the soil can be altered by the addition of LIME (makes the soil more alkaline) or sulfur (makes the soil more acid).  But the changes are only temporary as the soil tends to revert to the original pH level.

Presently work is being done in order to obtain the optimum fertility level for trees (Roger C. Funk, Ph.D. with the Davey Tree Expert Company in Kent, Ohio).  On the other hand, a report in the April 1995 issue of Arbor Age "Nitrogen Fertilizer and Beyond" by Stuart Warren, Ph.D. North Carolina State U in Raleigh, recommends no additional N at planting time.

MATCHING THE RIGHT TREE WITH THE RIGHT AMOUNT OF SUN. Do you know, for instance, that the dogwood, the rhododendron and the hawthorn are UNDERSTORY TREES i.e. they developed their system in the shade?  Full sun makes them susceptible to pest and fungus problems, e.g. the anthracnose problem in Pennsylvania.  To compound the problem further, some people also plant grass and flowers under the trees, prune improperly, apply agricultural fertilizers as if trees were a kind of corn, and the list goes on).  An example of a tree requiring full sun is the birch.  Later on we shall point out that it also requires an adequate amount of water.  Two other trees in this category are the sweetgum and the cherry.  Deprivation, again, leads to pest and fungus problems. You can learn how to do things right, read 100 TREE MYTHS by Dr. Alex L. Shigo.  Another good article to read is DON'T WORRY, PLANT A TREE by Ted Williams, Audubon, May 1991.

SYMBIOSIS IN PLANT LIFE.  In nature, animal life as well as plant life, different species often live together for mutual enhancement or even survival.  A notable example is the symbiosis between tree roots and a root fungus, MYCORRHIZA.  (The Greek words for fungus and root.)  Its function is to facilitate absorption of water and elements, mainly phosphorus.

There are basic types of mycorrhizae, the ectomycorrhizae which have their fruiting bodies above the ground, and the endomycorrhizae which have the fungus tissue within the soil inside the roots and cells.  Thus, oaks, beeches and pines, amongst others, which need the ecto-variety can be killed by soil compaction.  Conversely, trees like the maples, ash, elms and sycamores can survive under a blacktop because their endomycorrhizae does its fruiting underneath.  But it should be stressed that under any circumstances soil compaction may be hazardous to a tree's health.  In this connection let's remember not to plant grass near trees because mycorrhizae flourish in leaf compost while grass does the opposite.  Also to be considered are the future needs of the growing tree with its expanding roots.  In other words put mulch over a sufficiently wide area.  DON'T USE FRESH CHIPS.  ( Ref . Dr. Alex L. Shigo on Mycorrhizae and Mulch. )

Another important aspect of tree biology is the difference in "plumbing" i.e. the way water is transported, stored and used.  For instance, Oak, Elm, Chestnut, Robinia-Black Locust are ring porous trees.  In these, on cross section, you see the vessels quite large in the early spring, laid out in concentric circles, and copiously absorbing water in the early growth season after which they close down.  On the other hand, Maple, Sycamore, Honey Locust and Tulip Tree are diffuse porous trees with the vessels equally distributed over the cross section.  They take up water during the entire growth period.  The Birch also belongs in this group since it requires water and keeps its stomata open throughout. Conifers do not have vessels, they have tracheids.  Their water requirements are similar to the ring porous trees.  The reason for this is that the tracheids are at first thin walled and then become thick walled as the increment progresses.  Thus, one will choose the appropriate location for planting either of these groups according to the water supply.  But there are also trees, such as Ash and Mulberry, which are "semi-diffuse", not quite belonging to either category and developing tyloses, plugging of the vessels, irregularly.

The next article will be on Proper Selection and Planting of Healthy Trees.

John A. Keslick, Jr.
Tree Biologist

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