How To Maintain Healthy Trees

When Does a Tree Become a Risk?

Most trees in our landscapes are quite safe and pose no threat. However, some trees can become dangerous due to serious structural defects.

Recognizing these defects is often difficult for the untrained eye. Trees can appear perfectly healthy and green, yet pose a threat to people and property because of defects such as dead branches, cracks, weak branch unions, internal decay, cankers, root problems, or just poor form. Learning to examine and evaluate our trees and the severity of their defects can lead to corrective action that will reduce the likelihood of the tree falling and injuring someone.

How to Recognize a Hazardous Tree – an informative publication from the USDA Forest Service

Tree Diseases that Create Hazards – a Penn State Fact Sheet

Recognizing Tree Hazards, a ISA Publication for Homeowners

Storm Damage Resource Center – a USDA Forest Service Website

Storm Damaged Trees: Prevention and Treatment

Storm Recovery – National Arbor Day Foundation Website

Storm Damage and Hazard Evaluation Factsheets

Understanding What Could Be Causing Problems With Your Trees

Diagnosing plant problems can be a difficult task. To diagnose plant problems, you need to know how a healthy plant grows and have some knowledge of the stresses that affect plant health. You need an understanding of the plant’s normal appearance before you can begin to monitor for signs and symptoms of a problem.

Plant problems can be grouped into four major categories:

• Cultural – problems that arise from the care of the landscape, such as fertilizing, use of herbicides and pesticides, improper pruning, inadequate or over watering, improper planting, over mulching, etc
• Environmental – problems often out of our control, caused by nature, such as droughts, hail, lightning, high or low temperatures, floods, etc
• Diseases – plant problems that are brought about by infectious agents such as bacteria, fungi, nematodes and viruses. Common diseases include leaf spots, vascular wilts, cankers, and root rots
• Insects – plant problems caused when insects chew leaves, suck sap (plant food) from leaves and twigs, or borer into the stems. The vast majority of insects in our landscapes are not harmful to our plants and some are beneficial because they prey on harmful insects

When we first see a plant problem (e.g. chewed or distorted leaf), often our first impulse is to apply a pesticide without even knowing what caused the injury. We are usually wasting time and money, and sometimes causing more harm than actually solving the problem. Proper diagnosis of the problem is critical and takes knowledge of the plant and the pest. Often you might need some help from a landscape professional or have to bring a plant sample into your local arborist.

 

Dealing With Drought

Hot dry summers and winter winds can often cause damage to trees and shrubs. Drought reduces the amount of water available in the soil that trees can take up. Injury to the tree occurs when more water is lost through transpiration than is available in the plant.

Symptoms of drought stress include: wilting of foliage, sparse canopy of off-color and undersized leaves, leaf scorch, yellowing, and premature fall coloration. Closer inspection of the branches will reveal twig growth and small, poorly formed buds. Prolonged drought will cause branch and root death and dieback or death of the entire tree. De-icing salts and fertilizers can compound the situation burning root and leaf tissue. Drought stress often weakens trees, making them more susceptible to attack by some fungi (root rots and branch cankers), and wood-boring insects that come in to “finish off” a dying tree.

Some species of trees and shrubs are more susceptible to droughts, while others can withstand dry conditions. Trees such as maple, dogwood, ash, beech, linden, and tuliptree tend to be affected by droughts more than oaks, elms, and honeylocust. Newly transplanted trees are very susceptible t damage from dry soil conditions because they have lost approximately 90% of their root systems when they are dug and moved.

Preventing Drought Damage on Trees and Shrubs

Mulch Your Trees – applying a thin layer (3 inches) of mulch on the root systems out to the tips of the branches (dripline) mimics how trees grow in the forest and will help retain moisture in the soil.

Water – always water newly planted trees (rain or shine) on a weekly basis with approximately 10-20 gallons per inch diameter of tree. Put that water on the rootball, where it is needed and don’t just water the lawn with a sprinkler. Consider using water devices such as Treegators or Oozetubes to allow for slow deep soil watering on the root systems of newly planted trees. For older trees, mulching will help, but sometimes it is necessary to provide water to older trees to assure their survival. Using rain barrels and drip hoses will help you save money and recycle stormwater that impacts are streams. For healthy growth, trees require approximately 1 inch of rainfall each week.

Pruning and Fertilizing – During droughts, avoid pruning healthy live branches and fertilizing trees and shrubs. Prune dead wood only and use slow-release fertilizers to avoid drying out roots and promoting leaf growth that a stressed root system can not support

Pest Management – Scout for insect and disease problems on drought-stressed trees and shrubs. Look for cracks in trunks and branches, small holes in trunks where wood-boring insects emerged, sawdust or sap flow, and branch dieback. It is best to keep the tree healthy by mulching and watering than trying to control insects and diseases that are attacking a stressed plant.

Think Before You Top!

Topping is the senseless practice of indiscriminately removing a majority of a tree’s branches. Topping violates acceptable pruning practices, including National Tree Care Standards (ANSI A-300).

Many people think that topping will help their tree or make them smaller and safer, but in reality it is one of the worst things you can do to your tree! Topping does not make your tree safer. Topping actually creates a more dangerous tree because it opens branches up to decay and rot fungi, slowly weakening the tree internally, shortening its life, and causes future branch breakage and storm damage.

Pruning vs Topping

Pruning your tree is a double-edged sword. If done properly it can improve a tree’s health, form, structure and safety. But if it is done improperly (without an understanding of tree biology) it can be the worst thing you can do for your tree, causing stress, declining health, internal decay, un-safe conditions, and sometimes tree death. It all depends on how much you prune, and the types of cuts you make, or the professional you hire.

Before you prune your trees, get some advice from the local arborist office about proper pruning and how to select a qualified arborist, such as an ISA Certified Arborist.

Working Safely

Never climb a tree to prune it yourself. If you are not trained as a tree climber or have the proper equipment and insurance, it is very dangerous. Leave it to the professionals. Never prune or climb trees that have electric lines running through them. Call the local utility company when tree branches are touching overhead utility lines.

Go Easy With The Mulch

Mulching trees can be one of the most beneficial things a homeowner can do for the health of a tree. Mulch can reduce water loss from the soil, minimize weed competition and compaction, and improve soil structure, fertility and health. If applied properly, mulch can give landscapes a handsome, well-groomed appearance.

Problems occur when mulch is applied too thick and piled high on trunks and stems. Sometimes improper mulching looks like mountainous mulch volcanoes at the base of trees. When this is done, it creates a moist environment in which opportunistic decay fungi attack the trunk and roots, causing root rots, crown dieback, a decline in health, and tree failures. Over-mulching also prevents gas exchange, suffocating roots and stems; can lead to rodent chewing and stem girdling; nutrient deficiencies; and often causes roots to grow up into thick mulch, only to dry out in hot summers, or form girdling roots that encircle and kill trees.

When applying mulch, it is important that we not cover that trunk flare (taper) with soil or mulch. Spread the mulch out in a layer that is no thicker than 2-4 inches, and don’t pile it up on the trunks of trees and stems of shrubs.

Frequently Asked Questions

Trying to decide what should be done to your trees or who should do the work can be confusing for many homeowners. We want to help homeowners, municipal officials and the green industry learn more about trees and the proper care and maintenance of trees in our landscapes.

If our content has not clarified your questions, the following websites might help you explore some of the frequently asked questions about tree care.

Tree Care Industry Association’s Frequently Asked Questions about Tree Care websiteTree Care Industry Association’s Frequently Asked Questions about Tree Care website