Humans aren’t the only ones to be affected by ozone alerts in various parts of the country. Many of the most commonly planted trees in the nation’s urban forest also suffer during high levels of ozone pollution.
Ozone is the result of a chemical reaction that converts car exhaust into ozone in the presence of light. The regions that have the highest automobile traffic and sunshine are the most at risk. Even areas without congested traffic may suffer, since ozone is transportable over long distances. In southern California, entire populations of Ponderosa pine have been wiped out in the San Bernadino Mountains due to chronic ozone exposure. Surviving tree populations are made up exclusively of ozone-tolerant species.
The pollutant acts as an oxidant that disrupts the chemical pathways in a plant’s photosynthetic powerhouse, the chloroplast. In response, the tree manufactures antioxidants like vitamin E and C. This process may offer relief from low levels of ozone, yet are no match for repeated exposure to toxic levels.
Ozone injury looks different on different species. On the leaves of poplar and black cherry, the homeowner may see brownish lesions on a leaf that appears water-soaked. On ash and hickory, however, the lesions are white. On other species, damage appears as a purple stippling all over the leaf. Evergreens appear to have burnt needle tips.
At present, the best thing homeowners can do to protect trees from ozone injury is to keep them in an overall healthy state. This includes protecting trees from wounding, and keeping them well watered and judiciously fertilized.
Below is a list of sensitive and tolerant species:
| Sensitive: | Tolerant: |
| Yellow poplar | Hemlock |
| White ash | Eastern and Colorado blue spruce |
| Hickory | Yew |
| Black cherry | Rhododendron |
| Flowering dogwoods | Azalea |
| Eastern white pine | Oak |
| Sassafras | Most maples |
| Aspen | Balsam fir |
| London plane |
Homeowners who believe their trees may be suffering from ozone pollution should consult a professional arborist to monitor their trees. Certified Arborists will be able to suggest treatments to keep trees as healthy as possible, and if necessary, recommend ozone-tolerant species to plant around homes where the potential for ozone damage is high.
Contact Acorn Arboricultural Tree Service, a member of the Tree Care Industry Association (TCIA), a 65-year-old public and professional resource on trees and arboriculture. Acorn recognizes stringent safety and performance standards, and carries liability insurance.
Acorn Arboricultural Tree Service would be happy to consult with you about your tree’s health. Contact us to schedule a consultation with our staff of arborists Sacramento who can identify the causes of tree health problems and make recommendations for treatment or tree removal.
Contact Acorn Arboricultural Tree Service, Inc. with any additional questions or for a consultation using our online form or call us at 916-787-8733!