Friday, February 24, 2012

OPALS - How do your trees measure up?

In my last post I explained how poor judgement in planting all male varieties of trees has caused an increase in pollen in the air we breath, which in turn has caused allergies and asthma in children and adults to skyrocket. 

Of course, pollen isn’t the only thing causing increases in respiratory ailments. Automobile exhaust is another obvious culprit as is dust, tobacco smoke, animal dander, molds, and other airborne substances. Mold in particular is another significant source of increased allergy and asthma rates, and has become increasingly prevalent in the landscape as plant health has declined. Many trees and shrubs are unhealthy for a number of reasons, including poor placement in the landscape, poor or insufficient maintenance, storm damage, insect damage, and others. As their health deteriorates, many plants become vulnerable to attack by insects including aphids, scale, mealy bugs, and white flies. These insects secrete nutrient-rich feces, called honeydew, which attracts mold. The mold quickly reproduces creating millions of tiny spores which become airborne. Like pollen, these spores settle on our skin, eyes, noses, and throats. They can also reach our lungs and cause asthma. The American College of Asthma, Allergy and Immunology reports that asthma rates have exploded to the point that asthma is now the leading childhood chronic disease in America.

Excessive pollen and mold spores are actually considered pollutants.   It is predicted that allergy rates will continue to shoot upward and as a result the public will demand that all new city trees be planted are allergy free or at the very least are lower allergy selections.  Millions of people, urban children especially, will benefit from this switch, and it is really the best choice.  Remember, the reason for the excessive pollen is from planting mostly male trees to avoid "smelly and messy" landscapes.  And, let's not forget that planting mainly elms lead to a mass die off when Dutch Elm Disease struck.  

So, if we are to learn from our mistakes and prevent history from repeating itself, we know we can't decide to plant just one species of tree that is allergy free.   What not many of us know is that there actually is a rating system for evaluating the level of allergens produced by trees and shrubs called Ogren Plant-Allergy Scale (OPALS). This system rates plants from 1-10 with 10 being the most allergenic. It is currently used by the U.S. Department of Agriculture. With this system, land managers can determine how allergenic their plant lists are and make changes in order to limit this level.  It is a fact that some of the most widely planted street trees in Chicago have high allergenic rates, including Green ash males with a rating of 9 on the OPALS scale; Norway maple (8); Horse chestnut (7); Honeylocust males (7); Hackberry (8); Kentucky coffee tree males (9); and Linden (7). Experts believe that municipalities and private citizens alike should strive to plant plants that do not exceed a rating of 3-4 on the OPALS scale. However, this is easier said than done. Once again, the propagation of male, low-litter trees and shrubs has been a nursery standard for decades, which means that an overabundance of urban trees and shrubs are male pollen-producers. So how do we reverse this trend?  It needs to start with landscape nurseries as well as city planners, landscape architects, land managers, and landscapers who order from them.  They all need to be aware of the consequences of their poor planting. Nursery owners especially need to be made aware that just offering male plant species contributes to unhealthy air in towns and cities.

However, even if this can be done, a measurable difference will not be seen in pollen levels for at least a couple of decades, as female flowering and fruiting trees and shrubs gradually replace the pollen producing males. Reversing this trend can begin by doing three things: first, incorporate appropriate native plants into home landscapes; second, ask for a variety of male and female tree and shrub types from landscape and garden centers; third, maintain landscapes in order to retain good plant health for trees and shrubs. We can also support stronger clean air legislation and healthier living in general which will lead to healthier landscapes for both plants and people.

Plant health care is something we take very seriously at Trees "R Us, Inc.  We have 4 certified arborists on staff to diagnose, treat and prevent diseases in trees and plants.  You should consider having your plants and trees assessed by Trees "R" Us, Inc. to ensure they last for years to come and aren't contributing to the allergens we breath, like mold.  Trees "R" Us, Inc. can be contacted via the web at or by phone at {847}913.9069 or email at

Thanks for reading,

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