Physiology / Biology

1. Tree roots systems extend deep below the ground.

The large supporting root system near the base of the tree tapers rapidly into smaller roots, with the vast majority of all roots being concentrated in the upper few inches of soil. While a few roots may extend as deep as several feet, it is rare for many to exist at significant depths (more than a few feet). Therefore, protecting these upper layers of soil is critical to maintaining tree health.

2. I should buy the tallest or bushiest tree I can find at the nursery to get the most for my money.

The tallest tree may actually be weaker than smaller specimens in the same size container. While aesthetic features are important, tree trunk, branch and root system structure are far more critical to the long term success of the tree. Early structural ( trunk/branches) or root system problems are often the source of failure (breakage) of the tree many years later.

3. A good, strong, stake with strong ties is crucial when planting a tree.

While some nursery stock may require staking to remain upright, a tree that is capable of standing on its own should not be routinely staked. Improper or unnecessary staking can create problems that did not previously exist.

When faced with significant winds, or a weak specimen, proper staking may be necessary, and can make the difference in a success or failure. However, no type of support system can hold up a seriously defective tree indefinitely. Staking must be viewed and installed as a temporary assist while the tree develops its own strength, and then removed as soon as possible.

Pruning and Tree Maintenance

4. Pruning trees or shrubs invigorates them.

Pruning, particularly severe pruning, often results in the stimulation of dense, vigorous sprout growth. However, this production of vigorous growth consumes great amounts of the tree’s limited energy, weakening it’s natural defenses.

While the benefits of pruning are many, there is always some negative impact from the loss of foliage. Reduction of the foliage mass, however small, means a reduction in the tree’s capacity to photosynthesize, thus reducing the energy available for all its life processes.

Progressive techniques can maximize the benefits of pruning while minimizing the negative impacts. Conversely, improper or severe pruning maximizes the negative impacts while realizing very little, if any, of the benefits of pruning

5. Topping: (the removal of the upper portion of a main stem

  • Topping reduces the hazard potential of tall trees.
  • Topping can improve the health or structure of trees in poor condition.
  • Topping healthy tree does no harm.
  • Topping, performed “correctly”, does not damage trees.

Regardless of technique, topping is always a serious injury to the tree and usually results in serious, long-term structural consequences. A few of the negative impacts of topping:

  • Serious decay at the topping cut and poorly attached re-growth rapidly resulting in increased hazard potential.
  • Reduction of the tree’s energy producing capacity and thus its ability to resist insect and disease problems.
  • Creates denser foliage crown through rapid re-growth requiring frequent maintenance for re-topping or restructuring.

6. Filling cavities in trees with concrete strengths and helps them heal

Filling cavities does not increase structural strength. The process may actually cause harm and increase decay. Generally, management of tree cavities is best left to the tree itself.

7. Making pruning cuts close to the trunk or parent limb will help the tree heal

Trees do not heal, in that they do not replace lost tissue, but only cover injuries (e.g., Pruning cuts) with new layers of wood. To minimize decay and promote closing of wounds, do not penetrate the tree trunk but retain the “branch collar” (the slightly raised areas surrounding the base of most branches.)

8. Installing cables, bolts or other hardware will render a hazardous limb or tree safe.

Sometimes, to preserve a substantial limb, trunk or entire tree it becomes necessary to provide additional support through the installation of hardware. The installation of cables, bolts and other hardware in trees is intended to reduce hazard potential only and does not permanently remedy structural weaknesses and is not a guarantee against failure. Such hardware must also be inspected periodically and adjusted or replaced as necessary.

Chemicals, Amendments and Other Materials

9. Tree seal/ paint (or other tree wound dressings) prevents diseases, decay, insect infestations, or will otherwise help the tree heal

Tree sealants (tar, paints, shellac, etc.; ) do not prevent disease, decay, insect infestations or promote closing of wounds. There is actually some evidence that such sealants may actually cause harm. Leave wounds open and allow the tree’s natural defenses to work as intended.

10. Applying a fungicide to a cavity or wound will prevent or stop decay.

Trees reduce decay by forming internal chemical barriers at the time of and after wounding. The effectiveness of this process depends on each tree’s genetic characteristics and health at the time of wounding. Treatments after injury (e.g., Tree paint, cutting out decay, chemicals, etc.) Do not assist this process or reduce decay and such attempts often result in additional injury.

11. Annual or regular spraying of my garden will control insects and diseases.

Both insects and diseases require timely, targeted efforts for effective management. The best management technique may not be complete eradication, as natural predators (birds, other insects, etc.) Require some food source to remain in the vicinity.

Routine spraying with board-spectrum materials not only will not effectively address most problems, but may kill many beneficial insects, fungi and may even effect birds and mammals.

12. If I use a strong enough pesticide or fungicide, I can cure any insect or disease problem.

There are no blanket chemicals or schedule that can control all the insects and disease problems your plants may encounter. In fact, many diseases of plants have no known chemical controls.

13. Adding good topsoil, soil amendments and fertilizers when planting or transplanting is crucial to a plant’s success.

To significantly improve poor soils, a very large quantity of amendment (additions such as sand, redwood mulch, etc.) would be required over a very large area. Amendments in the planting hole alone will likely have more negative effect than benefit.

It is far more critical to plant at the right depth, in the right location for the species and to provide adequate (but not excessive moisture. Dig a planting hole several times wider than the root ball, and cultivate (break-up) the native soil before backfilling.

14. I can add soil around my trees as long as it is good quality topsoil.

It is critical that the base of trees remain at the appropriate depth in relation to the surrounding soil grade. Excessive soil, grade changes and root loss from excavations or frequent cultivation all have serious consequences and can result in tree decline or death.

15. I must use citrus fertilizer on my lemon tree, rhododendron food for my ‘rhodees’, rose food for my roses and lawn food for my lawn.

The elemental make-up of fertilizers does not change according to promotional labels. The primary element in fertilizers is nitrogen, followed by potassium and phosphorus. Nitrogen is used in large quantities by all green plants and is the only element that produces significant plant response. The fertilizer with the largest proportion of nitrogen is the best buy, regardless of the name on the label (plant’s can’t read!).

16. If I apply enough fertilizers, pesticides, and fungicides to my plants they will be healthy (all plant problems can be cured with chemicals).

All the chemicals, fertilizers and miracle plant drugs in the world cannot cause a plant to thrive in an inappropriate or inhospitable environment. Select a species that is appropriate for the climate and environment, with characteristics compatible with that environment, that will fulfill the desired functions as long as possible. Once established, concentrate on preserving that environment and protecting plants and locale from disturbances of any kind.

17. Trees flourish in the forest without maintenance, so they don’t need it in my front yard either!

Urban trees are required to contend with many negative influences not encountered by forest trees: limited rooting areas, confined spaces, pollution, soil compaction, asphalt and concrete over roots, etc.

Besides, an occasional dead tree in the forest is not noticed among the many, but the loss of one significant landscape tree can be devastating to your home.

18. If I prune and fertilize that massive pine tree in my font yard, it will be safe and live forever!

All trees of significant size that exist in proximity to people, structures, or vehicles or even other valuable landscape features represent some degree of hazard potential, regardless of their condition.

19. I can kill my neighbor’s annoying tree by driving a copper nail in the trunk when he’s on vacation.

Not only is a copper nail not only not going to kill the tree, but it is a primary components of many fungicides.

20. He advertised in the yellow pages as a tree expert, so he must be! Doesn’t some government agency monitor that sort of thing?

Anyone can put an ad in the Yellow Pages or call themselves a “tree expert”. Begin by calling only ISA Certified Arborists. Obtain at least several references and follow-up. Consider hiring a Consulting Arborist in advance for advice on what’s needed.

Always require insurance certificates and a detailed, written contract.


The worst enemy of trees is people! Damage to trees is only occasionally intentional, more often negligence, but most often occurs when intent is to provide conscientious care. Get progressive in caring for your trees!