(Editor's Note: This article was originally published on April 20, 2009.)
The 80-year-old silver maple pictured here suffered under the wrath of Hurricane Ike. When a large limp snapped off like a matchstick, the wound revealed the inner signs of aging: a hollow trunk and rot in places. The answer was clear: take the tree down, as it would never be healthy enough to survive. We did not replace it, since the mature grove of trees in which it stood provides so much shade that a young new tree would have a difficult time thriving.
Many factors affect our trees and shrubs during their lifetimes: age, weather, soil conditions, drought, physical damage, insects and disease, and all too often, human-induced stress. Some of these can be corrected with the probable result of bringing a tree or shrub back to health and longevity. Other factors cannot be controlled, such as drought, storms, and age.
Making Decisions to Save and Protect
For specimens affected by controllable factors, determine the extent of the stress or damage, then assess the value of the tree or shrub, either in terms of monetary, aesthetic, or sentimental. If you can save it, do so--especially mature elements that would leave a very bare spot in your landscape.
Soil Conditions: Most woody ornamentals and trees will thrive only if the soil conditions are correct for the species. When one of these begins to fail and you can find no other reason, consider testing the soil as far out as the drip line to ascertain whether the soil still meets the plant's requirements. If the soil pH needs adjustment, follow your local extension's guidelines for amendment. Sometimes, the soil has simply lost all its nutrients through rainfall and runoff over the years. Special fertilizers and organic mulch can often help boost the nutrients available to the roots.
Drainage: Poor drainage of runoff can result in overly wet conditions. Most roots will not grow in an area that is constantly wet. If you suspect that water is pooling underground in an area, dig several hole measuring a foot deep and a foot wide. Fill the holes with water; if the water has not drained within 24 hours, it means the area is saturated. Drainage tiles can be installed to improve this situation. Additionally, a rain garden can be situated in an area close by, and the runoff from gutters directed toward that instead of the natural contour of the land.
Physical Damage: Except in the instance of weather related stressors, most damage can be prevented with a little forethought.
- Lawn mowers and string trimmers are not a tree's best friend. Once cambial tissue on the trunk is damaged, the tree or woody ornamental is open to infestation by insects or disease. Mowing over exposed roots is another bad practice.
- Tree limbs or shrubs that rub against a building can be damaged, so trim away small limbs and branches, and cut back larger ones.
- Over-mulching creates perfect conditions for fungal growth at the base of a tree or shrub. Use no more than 2-3 inches of mulch, and keep it at least 3-6 inches away from the trunk.
- Exposed roots should never be covered with soil; this suffocates them by obstructing drainage, and air and water penetration, causing eventual death of the tree.
- Construction and landscaping can damage tree roots not only by cutting them, but also by compacting the soil. Pore space is needed for the exchange of gases, and compacted soil lacks this important feature.
- The root systems of trees and shrubs are in the upper 12 inches of soil and are therefore easily damaged by toxic spills. Household cleaning products, car washing compounds, cleaners for vinyl siding and patio furniture, petroleum products, lawn care products (especially those containing dicamba), and herbicides are just a few of the chemicals that can be taken up into the roots. Use prudence when applying herbicides and weed killers and, when possible, use organic methods of control. Choose environmentally friendly car care products and washing solutions for decks, furniture, and siding. Our landscape plants notwithstanding, these products also eventually end up in the groundwater.
- Insects & Disease: Healthy plants seldom fall prey to insect infestation or disease, but being in tune and on top of your trees and shrubs on an on-going basis will alert you to any signs of these problems. Use as many organic and earth-friendly management practices as you can to reduce destructive insect populations. Manage broken limbs and damaged trunks to prevent the occurrence and spread of disease. Be aware of what diseases and insect pests are of danger to your trees and shrubs.
What if it's Out of Our Hands?
Weather: Some weather related damage can be prevented or minimized by preparing certain plantings for the usual weather events in your area. For in-depth information on this type of preparation, read "Winter's Wrath: Ice and Snow Damage."
Many areas use salt on the roads to provide safe driving conditions. Unfortunately, the salt is detrimental to our landscape shrubs and trees. If you live in an area where salt is the choice for winter road maintenance, chances are you've seen the brown, dry evidence of salt intake on foliage that sits near a road. Avoid piling snow near your shrubs or trees. Find alternative melting methods for driveways and walkways, such as sand, cat litter, or sawdust. In early spring, flush the soil around the plantings with at least 2 inches of water for 2 to 3 hours, then repeat three days later.1 This will remove much of the accumulated salt from the soil. If the plants show signs of having been sprayed with salty water, rinse the foliage and branches thoroughly.
During drought conditions, be sure to water heavily and often. The ground surface becomes hard and resistant to absorbing water, so as soon as the dry weather comes, be vigilant.
Age: As with all things, the life cycle of a tree or shrub will come to an end. Monitor your oldest specimens to be aware of when they begin to fail. Increase in broken or dead limbs, poor leafing in spring, signs of rot in the trunk: these are the red flags that tell you a specimen is reaching the end of its lifespan. If a tree is close to your home or power lines, or even in close proximity to a neighbor, consider the consequences of that tree coming down in a storm. Have an arborist take a look and be confident in any recommendations he or she might make.
It's heartbreaking to lose a beloved tree or shrub, but in the life of a garden, this is a reality. Use every resource available to you to make the decision to save or replace your landscape elements.
1 Virginia State University, Virginia Cooperative Extension, Bulletin 426-500, 2001