In the Introduction, Ogren states:
... The concept-the soul-of this book is simply that through research, common sense, and knowledge, we can create fabulous landscapes and gardens that will not make us, our children, or our neighbors sick. As gardeners, we can control what we plant and dramatically limit allergens in our own yards. [page xvi]
He studied the topic for a decade and created the Ogren Plant-Allergy Scale (OPALS) which rates plants on a scale of 1 to 10 for their potential in causing allergies. This scale is the first of its kind available to landscapers or gardeners. The United States Department of Agriculture is now implementing the use of this scale to determine allergy ratings for our urban environments. Each city is analyzed for the variety of species grown within its boundaries. The number of trees of each species is included. Multiply the total biomass of each species by it's allergy rating to get a numerical rank for the city. Perhaps in the near future, people deciding to move to another area will be able to determine that city's allergy rating in addition to the quality of its schools, shopping, cost of living and other factors.
The book is divided into two sections. The first section discusses Ogren's personal beliefs about why allergies are on the rise. He blames it on two factors: (1) the dramatic increase in air pollution and (2) an increase in the use of "male only" plants which produce plenty of pollen but no seeds to clean up each year. He also discusses "volatile organic compounds" which are released by some trees. These are compounds that create hydrocarbons, one of the major components of smog and air pollution, when they are combined with sunlight and nitrogen. Most of us have never heard of these substances. We have been taught that we should plant more trees to help clear up air pollution. However, the fact that some trees actually cause smog and air pollution is not mentioned very often and certainly is not generally known by the public.
